Permafrost in Canada’s Subarctic Region of Northern
Ontario.
by
Andrew Tam
A thesis submitted in conformity with the requirements
for the degree of Masters of Science
Graduate Department of Geography
University of Toronto
© Copyright by Andrew Tam (2009)
ii
Abstract
An investigation of permafrost (permanently frozen soil) was conducted in
Canada‟s subarctic region of Northern Ontario. Environmental baseline conditions and
permafrost states were estimated using seasonal freezing and thawing energies based on
observed climate data and the Stefan equation. Field studies provided measurements of
the active layer depths and validated the permafrost states; laboratory studies of the soil
samples provided characterization for organic materials that have high affinity for soil
moisture. Palsas (unique dome-like formations) were observed to have enhanced
permafrost cores beneath a thermal insulating organic layer. With climate change, results
suggest the possibility of shifts from the classification of continuous to discontinuous
permafrost states in areas lacking the presence of organic materials that can have
environmental and ecological impacts. Northern infrastructures may become destabilized
with the degradation of permafrost while palsas may become lone permafrost refuges for
biodiversity that depend on cooler ecosystems, such as polar bears.
iii
Acknowledgments
Foremost, I would like express sincere gratitude to my supervisor, Prof. William
Gough, for his valuable assistance, guidance, professional knowledge, and most of all, for
his patience. I thank him for giving me the opportunity to grow as a student, to participate
in pursing a Masters degree, and to take responsibility in encompassing a research of this
scope.
I would like to recognize the assistance of Martyn Obbard and his personnel at the
Ontario Ministry of Natural Resources for this unique opportunity to study permafrost in
all of Northern Ontario.
I would like to acknowledge and express my gratitude to my fellow colleagues
Muaz Nasir and Joyce Zhang for their continuing and unwavering moral and academic
support and, in many instances, for providing me with reassurances throughout my years
at the University of Toronto at Scarborough.
I would like to recognize the contributions of Slawomir Kowal for his time in
preparing temperature data and for his assistance in the laboratory. I would like to give
special thanks to S. Das, J.W. Cowan, T.R. Beeby and A. Sarwari for their auxiliary
support in conquering the battle of proofreading my thesis.
I would like to extend special thanks to my parents for all their love, help and
support in my endeavours. I would like to show appreciation to my brother, Charles
Tam, and my sister-in-law, Angela, for all their continuing encouragements, support and
faith in my abilities. Finally, I would like to thank all my friends and supporters in
Trenton and Toronto whom continue to cheer me on in my life.
Funding from the Department of Geography at the University of Toronto
supported this research and funding by the Ontario Ministry of Natural Resources
supported the fieldwork.
iv
Table of Contents
Abstract …………………………………………………………………… ii
Acknowledgements .……...…………………………………………………… iii
Table of Contents …………………………………………………………… iv
List of Figures …………………………………………………………………… vi
List of Tables …………………………………………………………………… vii
CHAPTER 1: Introduction …………………………………………………… 1
1.1 Project Description …………………………………………… 1
1.2 Aim, Objectives and Hypotheses …………………………………… 3
CHAPTER 2: Literature Review …………………………………………… 5
2.1 Introduction …………………………………………………… 5
2.2 Surface Vegetation and Active Layer …………………………… 6
2.3 Permafrost …………………………………………………… 8
2.3.1 Defining Permafrost …………………………………… 8
2.3.2 Formation and Degradation Processes …………………… 10
2.3.3 Soil Moisture Content and Thermal Conductivity …… 12
2.3.4 Stefan Depth and Permafrost Table …………………… 15
2.3.5 „Thermal Offset‟ …………………………………… 16
2.4 Palsa …………………………………………………………… 17
2.4.1 Defining Palsa …………………………………………… 17
2.4.2 Physical Properties of Palsas …………………………… 18
2.4.3 “Palsa Lifting” …………………………………………… 20
2.4.4 The Palsa Cycle …………………………………………… 20
2.5 Soil Temperatures and Net Radiation …………………………… 22
2.6 Ground Heat Flux …………………………………………… 23
2.7 Geophysical Detection of Permafrost …………………………… 24
2.7.1 Ground Temperature Borehole Logging …………… 25
2.8 Literature Summary …………………………………………… 26
CHAPTER 3: Experimental Design and Methodology …………………… 30
3.1 Location and Study Site Descriptions …………………………… 31
3.1.1 Biogeography …………………………………………… 32
3.1.2 Climate Data and Weather Stations …………………… 34
3.2 Field Experimental Design …………………………………… 35
3.2.1 Soil Temperatures and Thermistor Probes …………… 35
3.2.2 Point-scale Geophysical Sampling …………………… 35
3.2.3 Sample Labelling and Identification …………………… 38
3.2.4 Field Soil Characterization …………………………… 39
3.3 Laboratory Analytical Methodology …………………………… 39
3.3.1 List of Materials …………………………………… 39
3.3.2 Laboratory Soil Characterization …………………… 40
3.3.3 Gravimetric Soil Moisture Content …………………… 41
v
3.3.4 Soil Acidity, Average pH Value …………………… 43
3.3.5 Soil Moisture Content Loss Test …………………… 43
3.4 Stefan Depth and Permafrost Table Calculations …………………… 45
3.5 Thawing and Freezing Degree-Days Calculations …………… 46
3.6 Geographical Information Systems …………………………… 47
CHAPTER 4: Results …………………………………………………… 48
4.1 Climate and Environmental Data …………………………………… 48
4.2 Soil Characterization (2007-2008) …………………………… 49
4.3 Laboratory Analysis Results (2007-2008) …………………… 58
4.3.1 Soil Moisture Content and Soil Acidity …………………… 58
4.3.2 Measured Depths to Permafrost …………………………… 61
4.4 Freezing and Thawing Degree-Days (1989-2007) …………… 64
4.4.1 Results from 1989 to 2002 …………………………… 64
4.4.2 Results from 2004 to 2007 …………………………… 66
4.5 Stefan Depth and Permafrost Table Results (1989-2007) …… 68
4.5.1 Porous Sandy Soils (1989 to 2007) …………………… 70
4.5.2 Non Porous Sandy Soils (1989 to 2007) …………… 72
4.5.3 Clay Soils (1989 to 2007) …………………………… 74
4.5.4 Peat and Organic Materials (1989 to 2007) …………… 77
4.6 Soil Moisture Content Loss Test (2008) …………………………… 81
CHAPTER 5: Discussion …………………………………………………… 82
5.1 Soil Characterization …………………………………………… 82
5.2 Freezing and Thawing Degree-Days …………………………… 85
5.3 Stefan Depth and Permafrost Table …………………………… 86
5.4 Permafrost Presence …………………………………………… 89
5.5 Palsa Presence …………………………………………………… 93
5.6 Addressing Research Question 1 …………………………………… 94
5.7 Addressing Research Question 2 …………………………………… 97
5.8 Sources of Error and Uncertainties …………………………… 98
5.9 Potential Research Impacts on Society …………………………… 101
CHAPTER 6: Conclusion …………………………………………………… 103
6.1 Permafrost …………………………………………………… 103
6.2 Palsas …………………………………………………………… 105
6.3 Recommendations for Further Research …………………………… 106
References …………………………………………………………………… 108
APPENDIX – Additional Figures …………………………………………… 115
vi
List of Figures
Figure 1 – “Baby” Palsa in Northern Ontario, August 2007 …………………… 18
Figure 2 – Location of settlements, weather stations and rivers
in Northern Ontario …………………………………………………… 30
Figure 3 – Terrestrial Ecozones for the Hudson Bay Lowlands by Natural
Resources Canada (Natural Resources Canada, 2007) …………… 32
Figure 4 – Forested Ecozones for the Hudson Bay Lowlands by Natural
Resources Canada (Natural Resources Canada, 2003) …………… 33
Figure 5 – Sampling Sites located in Northern Ontario Hudson Bay
divided by Three Quadrants from both 2007 and 2008 Soil
Sampling Campaigns …………………………………………………… 36
Figure 6 – Sampling Sites located in Northern Ontario - Hudson Bay for 2007
divided by Three Quadrants …………………………………………… 37
Figure 7 – Sampling Sites located in Northern Ontario - Hudson Bay for 2008
divided by Three Quadrants …………………………………………… 38
Figure 8 – Labeled sample bag with associated tin foil tray container …… 40
Figure 9 – Analysis of soil sample D5a …………………………………… 41
Figure 10 – Subsurface stratigraphy classification of Northern Ontario
and Hudson Bay by Natural Resources Canada
(Natural Resources Canada, 2006) …………………………………… 48
Figure 11 – Results: Freezing and thawing degree-days for Peawanuck,
Ontario, from 1989-2002 …………………………………………… 64
Figure 12 – Results: Freezing and thawing degree-days for Peawanuck,
Ontario, from 2004-2007 …………………………………………… 66
Figure 13 – Thermal conductivity to water content for fine-grained soils,
both frozen and thawed soils (Nixon & McRoberts, 1973) …………… 69
Figure 14 – Thermal Offset for Sand (Porosity >0.33)
Compositions 1989-2007 …………………………………………… 70
Figure 15 – Thermal Offset for Sand (Porosity <0.33)
Compositions 1989-2007 …………………………………………… 72
Figure 16 – Thermal offset for Clay Compositions 1989-2007 …………… 75
Figure 17 – Thermal Offset for Peat Compositions 1989-2007 …………… 77
Figure 18 – Thermal Offset for Palsa (Dense peat)
Compositions 1989-2007 …………………………………………… 79
Figure 19 – Excavated Palsa located in a vegetated region
in Northern Ontario …………………………………………………… 115
Figure 20 – Soil Samples baking in the oven at 105˚C for gravimetric
soil moisture content analysis …………………………………………… 115
Figure 21 – Three male polar bears in Northern Ontario, August 2007 …… 116
vii
List of Tables
Table 1 – Methodology: Environment Canada Weather Station Information
with Climate, World Meteorological Organization (WMO)
and Transport Canada (TC) ID codes …………………………………… 34
Table 2 – List of Required Materials for Laboratory Analyses: 2007 & 2008
Sampling Campaigns …………………………………………………… 40
Table 3 – Results: Elevation and Annual Temperature Ranges in Northern
Ontario communities from Environment Canada …………………… 49
Table 4 – Results: Site & Soil Characterizations from 2007 Soil Sampling Campaign with
Distances from the Shores of Hudson Bay to the Sample Sites …… 50
Table 5 – Results: Site & Soil Characterizations from 2008 Soil Sampling Campaign with
Distances from the Shores of Hudson Bay to the Sample Sites …… 53
Table 6 – Results: 2007 Laboratory Analysis for Gravimetric Soil Moisture
Content and Acidity for Northern Ontario …………………………… 58
Table 7 – Results: 2008 Laboratory Analysis for Gravimetric Soil Moisture
Content and Acidity for Sampling Sites along the Shores
of Hudson Bay …………………………………………………… 60
Table 8 – Results: 2008 Laboratory Analysis for Gravimetric Soil Moisture
Content and Acidity for Sampling Sites inland in
Northern Ontario …………………………………………………… 61
Table 9 –Results: Depths to Permafrost for 2007 Sampling Site and Classified
By Quadrants …………………………………………………………… 62
Table 10 – Results: Depths to Permafrost for 2008 Sampling Site and Classified
by Quadrants …………………………………………………………… 63
Table 11 – Results: Yearly Average Depths to Permafrost per Quadrant …… 64
Table 12 – Results: Statistical Analysis of the 1989-2002
Peawanuck Degree-Days …………………………………………… 65
Table 13 – Results: Statistical Analysis of the 2004-2007
Peawanuck Degree-Days …………………………………………… 67
Table 14 – Results: Stefan Depths for Porous Sand (Porosity >0.33)
Soil Compositions (1989-2002) …………………………………… 70
Table 15 – Results: Stefan Depths for Porous Sand (Porosity >0.33)
Soil Compositions (2004-2007) …………………………………… 71
Table 16 – Results: Stefan Depths for Non-Porous Sand (Porosity <0.33)
Soil Compositions (1989-2002) …………………………………… 73
Table 17 – Results: Stefan Depths for Non-Porous Sand (Porosity <0.33)
Soil Compositions (2004-2007) …………………………………… 74
Table 18 – Results: Stephan Depths for Clay Soil Compositions
(1989-2002) …………………………………………………………… 75
Table 19 – Results: Stefan Depths for Clay Soil Compositions
(2004-2007) …………………………………………………………… 76
Table 20 – Results: Stefan Depths for Peat Compositions (1989-2002) …… 78
Table 21 – Results: Stefan Depths for Peat Compositions (2004-2007) …… 78
Table 22 – Results: Stefan Depths for a Palsa Formation (1989-2007) …… 80
Table 23 – Results: Soil Moisture Content Loss Test (2008) …………… 81
1
CHAPTER 1: Introduction
1.1 Project Description
The formation of permafrost in the Canadian subarctic, particularly in Northern
Ontario, is not widely understood considering the complex relationships between
environmental and physical factors (Brown, 1973; Waelbroeck, 1993; Hinkel et al., 2001;
Gough & Leung, 2002; Martini, 2006; Shur & Jorgenson, 2007; Kuhry, 2008). For
continuous permafrost presence in a region, climate conditions must be favourable. The
presence of permafrost can be determined from climate conditions by calculating the
Frost Number using freezing and thawing degrees-days (Nelson & Outcalt, 1987; Hughes
& Braithwaite, 2008). Based on a hypothesis proposed by Gough and Leung (2002), the
influence of soil thermal conductivity in enhancing the penetration of freezing and
thawing energies in permafrost, the “thermal offset” phenomenon, is the primary focus of
this research. In Gough and Leung (2002), sites in southeastern Hudson Bay followed the
Frost number threshold for continuous permafrost classification. For the southwestern
sites of Hudson Bay, the Frost number showed inconsistency with the field observations
of continuous permafrost. Gough and Leung (2002) first proposed possible errors in
calculations of the thawing degree-days utilized in the Frost number equations. Results
from Gough and Leung (2002) concluded that the possible errors such as overestimations
in the thawing degree-days due to the usage of monthly means instead of daily
temperatures and the influence of snow cover could not account for the inconsistency.
Gough and Leung (2002) proposed that the inconsistency could be explained by the
asymmetric thermal properties of frozen and unfrozen soils, the 'thermal offset'
phenomenon between different thermal conductivities that are strongly dependant on soil
2
moisture content. For this research, the concept of the penetration of freezing energy into
the soil column refers to a negative heat flux of energy in the soil column resulting in the
freezing of soils. The concept of the penetration of thawing energy into the soil column
refers to a positive heat flux of energy into the soil column that results in melting of
frozen soils.
Temperature data was collected from weather stations in the study area for the
calculations of the degree-days, which provided the climatological data needed for the
Stefan equation in calculating freezing and thawing depths and thus the thermal offset for
the region. Soil samples were retrieved by fieldwork from sampling sites along the shores
of Hudson Bay and inland in Northern Ontario. Published literatures on permafrost were
reviewed to establish relationships between soil moisture content and thermal
conductivity (Gross et al., 1990; Waelbroeck, 1993; Peck & O‟Neill, 1995; Henry, 2000;
Hinkel et al., 2001; Ling & Zhang, 2004; Carey et al., 2007; Shur & Jorgenson, 2007;
Zhang et al., 2008a; Christ & Park, 2009; Duan & Naterer, 2009; Nicolsky et al., 2009;
Wang et al., 2009). Laboratory analysis of the soil samples provided gravimetric soil
moisture contents, soil characteristics, and soil acidity. Characterizations and descriptions
of the soil samples were conducted to determine the presence of soil organic matter and
soil composition. Application of geophysical methods in detecting permafrost and
monitoring changes in ground temperatures are discussed in this research (Kurfurst,
1992; Kneisel et al., 2008; Nicolsky et al., 2009).
With climate warming affecting the subarctic regions, shifts in thermal properties
can produce unfavourable environmental conditions that can shift permafrost states
(Zoltai & Witt, 1995; Hayashi et al., 2007; Shur & Jorgenson, 2007; Kuhry, 2008; Wang
3
et al., 2009). Potential impacts from shifting permafrost states are further discussed for
civil infrastructures in northern communities and on the biodiversity that rely on the
current environment (Vyalov et al., 1993; Sorochan & Tolmachev, 2006; Jin et al., 2008;
Duan & Naterer, 2009).
1.2 Aim, Objectives and Hypotheses
The aim of this research is to establish the state of permafrost and palsas in
Northern Ontario and the areas along the shores of Hudson Bay based on field
observations during the 2007 and 2008 soil sampling campaigns conducted by Gough of
the University of Toronto and Obbard of the Ontario Ministry of Natural Resources. The
two main research questions for this thesis are:
1. Can the distribution of permafrost in Northern Ontario be rationalized using the
relationship between soil moisture content and the frozen and unfrozen soil
thermal conductivities, “the thermal offset” as hypothesized by Gough and Leung
(2002)?
2. Does the presence of palsas affect the thermal conductivity of soil from the
surface cover down to the permafrost?
There are four objectives in this research:
The primary objective of this research is to examine the relationship between soil
moisture content and soil thermal conductivity through the phenomenon known as
„thermal offset‟ in determining the permafrost state in Northern Ontario and the areas
along the shores of Hudson Bay as hypothesized by Gough and Leung (2002).
4
The second objective of this research is to determine the gravimetric soil moisture
content and soil acidity in a laboratory setting of the combined 53 samples from retrieved
over a two year field sampling campaign, and on going, in Northern Ontario.
The third objective is the characterization of the active layer soil conditions based
on field observations of the soil sampling sites in Northern Ontario and the retrieved soil
samples from the 2007 and 2008 summer sampling campaigns; the results are to be
categorized spatially in quadrants and by shore and inland locations. Locations with the
presence of palsas are to be identified since the presence of palsas can affect the soil
thermal conductivity. The ecological importance of palsas is considered in relations to
polar bear (Ursus maritimus) activities at palsas.
The final and fourth objective of this research is to examine alternative methods
to traditional borehole measurements in determining the permafrost state in Canada‟s
Subarctic and Arctic regions with focus on geophysical methods & techniques such as
ground temperature borehole logging.
I hypothesize that there should be a relationship between permafrost distribution
in the study region and high soil moisture content. Higher soil moisture content increases
the soil thermal conductivity especially for frozen soils enhancing the downward freezing
effects in the active layer. I also hypothesize that the areas of high moisture content will
be in areas of high organic matter, such as peat, moss and small vegetations as this layer
is an effective insulator, thus enhancing the freezing effect. Finally, I hypothesize that
regions with high moisture content, high organic matter, and climate conditions
favourable to permafrost should be dominated with continuous permafrost formation.
5
CHAPTER 2: Literature Review
2.1 Introduction
Research has shown relationships between climatic and soil conditions, such as
surface temperature and the moisture content of soil that controls the thermal
conductivity of heat energy conducted through the soil column used to diagnose the
presence of permafrost (Waelbroeck, 1993; Hinkel et al., 2001; Gough & Leung, 2002;
Seppälä, 2003; Shur & Jorgenson, 2007; Kujala et al., 2007; Zhang et al., 2008b; Pang et
al., 2009; Wang et al., 2009).
The active layer above the permafrost is the section of soil that experiences
seasonal freezing and thawing cycles. The soil thermal conductivity has an important role
in determining the depths of freezing and thawing penetrations from the surface into the
active layer that contribute to the evolution of the permafrost. Physically based heat-
conduction models (such as the Stefan equation) have been applied using collected field
data to estimate seasonal thawing and frost depths (Nixon & McRoberts, 1973; Halliwell
& Rouse, 1987; Nelson & Outcalt, 1987; Anisimov et al., 1997; Gough & Leung, 2002;
Crepeau, 2006; Overduin et al., 2006; Hayashi et al., 2007; Guglielmin et al., 2008;
Hughes & Braithwaite, 2008; Kneisel et al., 2008; Zhang et al., 2008a).
Field sampling and surveys are conducted to monitor the presence of permafrost,
the thickness of the active layer and to determine the soil characteristics. Permafrost
presence can be determined by drilling boreholes into the subsurface until reaching the
permafrost table; this also allows for direct measurements of the active layer thickness.
Confirmation of the presence of permafrost can be accomplished by lowering thermistor
6
probes to measure soil temperatures; permafrost is deemed to be present when
temperature is at 0ºC freezing.
Vegetation and peat cover over the active layer is known to have a significant
influence on both soil thermal conductivity and soil moisture content. The presence of
this top layer allows further protection of the permafrost from climatic extremes
(Seppälä, 1986). Brown (1973), Seppälä (1986), Weidong & Allard (1995), Kujala, et al
(2007), Vallée & Payette (2007), and Kuhry (2008) have linked the influence of peat and
vegetation on enhancing the soil thermal conductivity with moisture content in the
formation of unique geologic mounds on the permafrost, known as palsas. The presences
of palsas were analyzed for the relationships between soil moisture content and the
thermal conductivity that governs the rate of permafrost thawing based on field
measurements (Seppälä, 1986; Kujala et al., 2007; Kuhry, 2008). While complimenting
traditional point-scale borehole samplings on determining permafrost, geophysical
methods can be applied to detect frozen soil, ice structures and sediment layers
(Moorman et al., 2003; Kneisel et al., 2008).
2.2 Surface Vegetation and Active Layer
Zoltai & Witt (1995) determined general trends of pH for bogs, fens and peat
wetlands in Northern Ontario. Fens are wetlands, region of saturated lands, that are
hydrologically influenced by mineral soil deposits (Zoltai & Witt, 1995; Price &
Waddington, 2001). The pH of wet rich fens is above 7.0, basic conditions, while the pH
of moderate-rich fens is acidic between pH 5.5 and 7.0 (Zoltai & Witt, 1995). Poor fens
and bogs are acidic with pH generally less than 5.5 from humic acid generated by
7
decomposition of the dominant Sphagnum species (Zoltai & Witt, 1995). The surface
vegetated layer above the soil column is composed of moss and lichen species, and when
partially decomposed over time in bogs, peat is produced (Dunne & Leopold, 1978;
Gross et al., 1990; Zoltai & Witt, 1995; Price & Waddington, 2001). Results from the
study of soil moisture content in Sphagnum species conducted by Yoshikawa et al.
(2004) suggested that soil thermal conductivity is sensitive to volumetric soil moisture
content. Volumetric soil moisture content is the volume of water per unit volume of soil;
this is also reflected as the in situ field capacity (Yoshikawa et al., 2004). Field capacity
is the amount of water held in soil after gravitational drainage. Thermal conductivity is a
measure of the ability for a medium to transfer heat energy by a gradient (Yoshikawa et
al., 2004). The difference in thermal conductivity of dry and moist moss condition is
about 1.5 folds; this allows moss on top of permafrost, specifically palsa features, to have
a significant impact in the freezing process (Yoshikawa et al., 2004). During the freezing
process, formations of ice lenses contribute to frost heaving (Guglielmin et al., 2008).
The process of frost heaving is favourable in ground material with high soil moisture
content with organic content (Guglielmin et al., 2008). Water conductive porosity,
interconnected pores in soils, contributes to increased soil water content that suggests
organic soils can store greater volumes of soil water (Carey et al., 2007). Typical organic
soils have 40 to 60% active pore space capable to hold water where active pore spaces
have diameters greater than 1x10-5
metres (Carey et al., 2007). Carey et al (2007) noted
that larger porosity does not imply greater hydraulic conductivity and the effects of
interconnected pores can contribute to soil moisture flow. Organic matter possess greater
affinity for water that increase the soil moisture content which in turn enhances the soil
8
thermal conductivity in allowing a greater freezing penetration, i.e. frost depth, and, at the
same time, insulation against climatic changes in the environment (Waelbroeck, 1993;
Zoltai & Witt, 1995).
2.3 Permafrost
2.3.1 Defining Permafrost
Permafrost is defined as ground material that remains below 0ºC for at least two
consecutive years, a definition based solely on temperature (Gough & Leung, 2002;
Smith & Burgess, 2002; Shur & Jorgenson, 2007). Permafrost is found below the active
layer, in the cryotic layer, as the soil in a perennial frozen state (Smith & Burgess, 2002;
Gough & Leung, 2002; Shur & Jorgenson, 2007; Muller, 2008). The surface energy
balance, soil moisture content and organic top layer determines the active layer depth
(Gough & Leung, 2002; Muller, 2008). The active layer depth varies throughout the
season due to the freeze-thaw cycle, as a response to the thermal gradient between the
atmosphere and permafrost (Hinkel et al., 2001; Smith & Burgess, 2002; Muller, 2008).
Climate factors affecting the active layer includes air temperature, annual surface
temperatures, extended periods of warming, thickness of overlying organic layer and the
presence of snow (Pang et al., 2009). Permafrost is classified under the Cryosol and
Gelisol soil orders due to the presence of cryogenic process such as cryoturbation and ice
segregation (Bockheim et al., 2006; Juma 2006).
Shur & Jorgenson (2007) have defined permafrost in a broad sense encompassing
time and climatic variation, where three conditions have been developed: the climate
favourable to permafrost, climate neutral to permafrost, and climate unfavourable to
9
permafrost. Permafrost is always present where climate is favourable to permafrost and is
characterized with the continuous permafrost zonation (Shur & Jorgenson, 2007).
Permafrost is present or absent in the climate neutral condition and is characterized with
the discontinuous permafrost zonation (Shur & Jorgenson, 2007). There is no permafrost
in regions where there is unfavourable climate condition for permafrost (Shur &
Jorgenson, 2007). Relict permafrost distributions can be observed in unfavourable
climate condition where special classification zones can be characterized such as subsea
and mountain permafrost (Natural Resources Canada, 2006).
Permafrost classification by Natural Resources Canada (NRCAN) is generalized
into continuous, extensive discontinuous, sporadic discontinuous, isolated patches and no
permafrost zones based on land surveys, borehole observations and temperature
isotherms (French, 1999; Natural Resources Canada, 2006). Continuous permafrost is
classified in areas dominated by 90 to 100% permafrost presence, and typically
characterized in areas with mean annual temperatures less than –6 ºC (French, 1999;
Natural Resources Canada, 2006). Extensive continuous permafrost is classified in areas
containing 50 to 90% permafrost presence (Natural Resources Canada, 2006). Between
the 10 to 50% permafrost presence range is classified as sporadic discontinuous
permafrost, and typically characterized in areas with mean annual temperatures less than
–1ºC (French, 1999; Natural Resources Canada, 2006). Less than 10% permafrost
presence in an area is classified as isolated patches of permafrost with mean annual
temperatures less than 0 ºC (French, 1999; Natural Resources Canada, 2006). No
permafrost is classified where there is no observed presence of permafrost.
10
In order to calculate and distinguish zones of continuous and discontinuous
permafrost, the Frost number (F) using only climatological data can be employed.
Continuous permafrost was calculated to have a Frost number threshold of greater than
0.67. Discontinuous permafrost would be expected at regions with Frost numbers less
than 0.67 (Nelson & Outcalt, 1987). The Frost number was defined by Nelson & Outcalt
(1987) as a dimensionless ratio of freezing and thawing degree-day sums:
F = [(FDD0.5
) / (FDD0.5
+ TDD0.5
)], (1)
where FDD is the freezing degree-days and TDD is the thawing degree-days, both
in Celsius. Degree-days provide a non-linear relationship between accumulation and
annual mean temperatures used in periglacial proxies for permafrost distribution (Hughes
& Braithwaite, 2008). Freezing degree-days are calculated by summing the degrees of the
number of days below a threshold temperature, such as 0 degrees Celsius. For thawing
degree-days, the similar approach in freezing degree-day calculation is applied with a
threshold of days with temperatures greater than 0 degree Celsius. However, the
definition of the Frost number threshold does not produce consistent results in the
Hudson Bay region, as seen in Gough & Leung (2002), where as the eastern sites of
Hudson Bay follows the Frost Number threshold and the western and southwestern sites
of Hudson Bay do not. The Frost number in the latter instance is below the continuous
permafrost threshold at odds with observations.
2.3.2 Formation and Degradation Processes
Permafrost formation occurs on all exposed surfaces in continuous permafrost
zones that are controlled by climate (Shur & Jorgenson, 2007). This is known as climate-
11
driven permafrost (Shur & Jorgenson, 2007). The climate driven permafrost can be
modified by the ecosystem, this is known as the climate driven, ecosystem-modified
permafrost (Shur & Jorgenson, 2007). This complex formation also relies on energy
balance, soil thermal properties, evapotranspiration, microclimates and incorporating
spatial variation in topography and time (Shur & Jorgenson, 2007). As vegetation
develops and peat accumulates, the depth of the active layer becomes saturated with
water, enhancing the soil moisture content (Hinkel et al., 2001; Shur & Jorgenson, 2007).
Frost is then allowed to penetrate further into the active layer, reducing the depth (Hinkel
et al., 2001; Shur & Jorgenson, 2007). At the same time, the initial active layer base
above the permafrost incorporates to the cryotic layer (Hinkel et al., 2001; Shur &
Jorgenson, 2007). The freezing process from the top of the active layer down to the
permafrost and up from the permafrost table in autumn is referred by Hinkel et al. (2001)
as the “zero curtain regime.”
As Shur & Jorgenson (2007) suggested, permafrost degradation is pronounced in
discontinuous permafrost zones due to climate change and disturbances on the surface.
Shur & Jorgenson (2007) discussed four mechanisms of degradation. First, vertical
degradation can arise due to a lack of protection from the surface ecosystem, an organic
insulating layer, with warmer climate and a positive ground heat flux. The second
mechanism of degradation can occur by the removal of protective insulating vegetation
above the active soil layer to expose the permafrost to a warmer environment (Shur &
Jorgenson, 2007). The third mechanism includes the lateral degradation of permafrost
that can occur from warming and influx of heat from adjacent lakes and groundwater
hydrology (Shur & Jorgenson, 2007). Finally, the degradation-aggradation of permafrost
12
adjustments can occur from shifts to the current environmental condition over the
landscape that results in an overall net change in the ground heat energy balance, such as
changes in snow and organic covers (Hayashi et al., 2007; Shur and Jorgenson, 2007;
Muller 2008).
2.3.3 Soil Moisture Content and Thermal Conductivity
Shur & Jorgenson (2007) suggested that permafrost without a surface organic
layer is the least thermally stable. Results from Karunaratne & Burn (2004) suggested
that the underlying soil thermal properties have greater influence than the influence of the
surface ecosystems. Hinkel et al. (2001) noted that arctic soils, in general, possess a layer
of organic material that has large porosity and high hydraulic conductivity. Soil thermal
properties can be altered by the soil texture and rates of evapotranspiration by plant life
that can influence the soil moisture content (Spielvogel et al., 2004). Evapotranspiration
is the transfer of moisture to the atmosphere by photorespiration of vegetation and
evaporation process that dominates soil moisture content (Dunne and Leopold, 1978). To
calculate thermal conductivity (λ) for the upper peat and organic layers, Hayashi et al.
(2007) suggested applying the de Vries Equation:
λ = (xwλw + kaxaλa + ksxsλs) / (xw+kaxa+ksxs), (2)
where: x is the volume fraction of water (w), air (a) & solid (s),
λ is the thermal conductivity (Wm-1
ºC-1
), & k is a weighing factor of porosity. The de
Vries Equation accounts for the soil moisture content and porosity that heavily influences
the soil thermal conductivity (Zhang et al., 2008a). The de Vries Equation allows the
partitioning of the three interfaces of water, air and solid (Hayashi et al., 2007, Zhang et
13
al., 2008a). Shur & Jorgenson (2007) suggests that with thermal conductivity properties
of the soil, permafrost would be expected in regions of silty and clayey soils, and seldom
in regions with gravely soils.
Conduction of heat energy through the soil column and permafrost can be
enhanced by an increase in water content resulting in a greater loss of heat during the
winter and greater heat retention in the summer (Shur & Jorgenson, 2007). Hinkel et al.
(2001) found that increased air temperatures does not directly increase the thermal heat
flux towards the permafrost through the active layer, but is a surrogate measure of the
overall net energy balance entering the ground. Hinkel et al. (2001) mentioned that
thermal energies, both freezing and thawing, entering the active layer can be dissipated
by near-surface evapotranspiration, as a function of the soil moisture content, initially
protecting the permafrost from thawing or degradation in the early spring and fall seasons
allowing for a time-lag in the freezing and melting process. With warming temperatures,
the increase in runoff and melt water can modify the topography through erosion and
affect the underlying permafrost by increasing the soil moisture content (Thie, 1974;
Cline, 1997; Hinkel et al., 2001; Spielvogel et al., 2004; Martini, 2006; Eyles, 2006;
Wang et al., 2009). Soil moisture content can be enhanced over time by the development
of drainage networks, increase in precipitation rates, decrease in evaporation rates, and
changes in the soil composition (Thie, 1974; Hinkel et al., 2001; Spielvogel et al., 2004;
Martini, 2006; Wang et al., 2009). The soil moisture content is associated with the
underlying soil texture as silty and clayey soils will have a higher water content yielding
higher thermal conductivities, and gravel soils will have lower water content, yielding
lower thermal conductivities (Peck & O‟Neill, 1995; Hinkel et al., 2001; Spielvogel et
14
al., 2004). Shur & Jorgenson (2007) observed that landscape regions of wet organic soils
typically had permafrost and landscape with gravely soils had discontinuous permafrost.
The evaporative cooling effect from high moisture content serves as a buffer against
temperature variation (Hinkel et al., 2001; Spielvogel et al., 2004). Over prolonged
periods of time in moist conditions, insulating peat can develop to provide further
buffering against temperature variation by increasing the thermal resistance, inverse of
the thermal conductivity (Thie, 1974; Hinkel et al., 2001; Cheng et al., 2004; Spielvogel
et al., 2004; Martini, 2006; Zhang et al., 2008b; Pang et al., 2009). Other environmental
factors such as snow cover can increase thermal resistance and insulate against warming
temperatures (Cline, 1997; Cheng et al., 2004; Osterkamp, 2005; Zhang et al., 2008b).
These complex thermal properties between the peat and snow layers can act to protect the
permafrost, keep the permafrost table stable and contribute to permafrost aggradation
(Cheng et al., 2004; Martini, 2006; Zhang et al., 2008b; Pang et al., 2009)
Field soil moisture content and thermal conductivity can be determined using
thermistor probes in soil pits (Halliwell & Rouse, 1987; Overduin et al., 2006; Hayashi et
al., 2007; Shur & Jorgenson, 2007; Nicolsky et al., 2009). For soil moisture content,
another common method is to employ a Time-Domain Reflectometry (TDR) probe at
specific depth intervals of the active layer (Halliwell & Rouse, 1987; Pilon et al., 1989;
Hayashi et al., 2007). Neutron probes and gravimetric soil moisture content methods can
be used to determine reference field values (Pilon et al., 1989; Hinkel et al., 2001;
Hayashi et al., 2007). Thermal conductivity can be determined using needle probes
buried at specific intervals of the active layer and record changes as the active layer
15
thaws (Halliwell & Rouse, 1987; Overduin et al., 2006; Hayashi et al., 2007; Nicolsky et
al., 2009).
2.3.4 Stefan Depth and Permafrost Table
Nixon & McRoberts (1973) derived the Frost depth calculation for estimating the
depth of active layer thawing and freezing with the thermal conductivities and
temperatures. The Frost depth (D) in metres, is represented by the general heat
conduction (flux) equation:
D = [(2nλtTave)/(ρƒL)]0.5
, (3)
where, λ, the thermal conductivity can be represented as λf, frozen thermal conductivity
in the winter season, and λu, the unfrozen thermal conductivity in the summer seasons, n
is the n-factor ratio between ground-surface to air temperature (dimensionless), t is the
elapsed time since thawing (s), Tave is the mean temperature (ºC), ρ is density of ice
(kgm-3
), ƒ is volumetric fraction of ice (dimensionless), and L is the latent heat of fusion
of ice (Jkg-1
; Nixon & McRoberts, 1973; Nelson, 1986; Broadridge & Pincombe, 1995;
Rees, 2006; Hayashi et al., 2007; Hughes & Braithwaite, 2008). This equation is also
known as the Stefan equation (Crepeau, 2006; Hughes & Braithwaite, 2008). A
simplified version of the Stefan Equation using degree-days is given as:
D = (2 λ DD/L)0.5
, (4)
where DD is the Degree-days, for freezing days in the winter, freezing degree-days
(FDD), and for thawing days in the summer, thawing degree-days (TDD).
To represent the summer Stefan thawing layer depth, the equation:
Du = (2 λu TDD/L)0.5
, is applied (5).
16
For Stefan freezing layer depth, the equation:
Df = (2 λf FDD/L)0.5
, is applied (6).
Criteria for a stable permafrost state, based on the Stefan depth calculations, occurs when
depths of freezing (Df) is greater than the experienced depths of thawing (Du) in a soil
column (Nixon & McRoberts, 1973).
2.3.5 „Thermal Offset‟
„Thermal Offset‟ is a phenomenon as arising from the difference in frozen and
unfrozen soil thermal conductivities in units Watts per meter degrees Celsius (Burns &
Smith, 1987). Burns & Smith (1987) characterized „thermal offset” as when a mean
annual temperature difference exists between the upper active layer and the permafrost
layer. Thermal offset is determined by soil thermal conductivity that in turn is associated
with soil moisture (Burns & Smith, 1987). Frozen soils as compared to unfrozen soils
have greater thermal conductivities (Kujala et al., 2007). In winter, frozen soils with high
soil moisture content allow for a deep downward penetration of cold energies that freezes
the soil (Burns & Smith, 1987; Anisimov et al., 1997). In summer, unfrozen soils with
low soil moisture content have reduced warming penetrations energies (Burns & Smith,
1987; Anisimov et al., 1997). For cold energy penetration, mean seasonal winter
temperatures are applied to the Temperature of Seasonal Depth of Thawing/Freezing
(Thermal Offset) equation:
Df = Du + ΔDλ (7),
where ΔDλ in metres is the thermal offset, difference in the thermal properties of the
frozen, winter, Df, and thawed, summer, Du, soils from Equations 5 and 6 (Nixon &
17
McRoberts, 1973; Burns & Smith, 1987; Anisimov et al., 1997). The application of the
thermal offset calculations provides a more robust method for determining permafrost
thickening and degradation over time due to the inclusion of the thermal conductivity
factor in the Stefan equation, Equations 3 to 6 (Anisimov et al., 1997).
2.4 Palsa
2.4.1 Defining Palsa
Palsas are geologic formations on continuous and discontinuous permafrost zones
in the subarctic regions possessing a permafrost core and alternating layers of segregated
ice that form lenses (Seppälä, 1986; Weidong & Allard, 1995; Kujala, et al., 2007).
Palsas have been observed in Canada, Finland, Iceland, Alaska and Siberia (Seppälä,
1986; Weidong & Allard, 1995; Kujala, et al., 2007; Vallée & Payette, 2007; Kuhry,
2008). In Canada, palsas have been documented in Northern Québec, Northern Ontario
and Northern Manitoba (Brown, 1973; Weidong & Allard, 1995; Vallée & Payette,
2007). Palsas appear as thick mounds or circular-domed elevation of terrain (Brown,
1973; Seppälä, 1986; Kujala, et al., 2007; Kuhry, 2008; Figure 1). These mounds can
have a height up to a few metres and diameters from tens to hundreds of metres and are
carbon pools due to the vast amount of organic materials (Brown, 1973; Seppälä, 1986;
Kujala, et al., 2007; Kuhry, 2008). Luoto & Seppälä (2002) classified palsas to be
typically present in flat areas adjacent to water bodies with the presence of organic
materials.
18
Figure 1 – “Baby” Palsa in Northern Ontario, August 2007. Photo by:
William Gough.
The internal core of the palsa is composed of frozen peat, silt and layers of frozen ice
(Seppälä, 1986). It should be mentioned that palsa research is limited to a few selected
authors (Brown, 1973; Seppälä, 1986; Weidong & Allard, 1995; Kujala, et al., 2007;
Vallée & Payette, 2007; Kuhry, 2008).
2.4.2 Physical Properties of Palsas
Palsas are usually found in regions of high acidic peat formation typically a bog
wetland (Brown, 1973; Seppälä, 2003). Kujala et al. (2007) determined physical
properties of the palsa mounds, peat was collected and the pH was determined to be 3.4
and the water content was 79% of the total mass by weight. Studies on palsa formation
and height by Seppälä (1986) suggested that during the summer season, the peat layer is
dryer and has a lower thermal conductivity. During the fall season, peat thermal
19
conductivity increases as freezing and water content increases in the peat (Brown, 1973;
Seppälä, 1986; Kujala, et al., 2007). This increase in peat thermal conductivity allows the
frost and cold to penetrate deeply into the palsa to enhance freezing of the ice lenses
(Kujala, et al., 2007; Kuhry, 2008). The presence of snowfall in the winter season tends
to decrease the thermal conductivity preventing the cold penetration effect (Kuhry, 2008).
Frost heave contributes to the dome-like feature of palsa from the freezing of soil
moisture in establishing the ice lenses (Seppälä, 1986; Henry, 2000; Kujala, et al., 2007;
Guglielmin et al., 2008; Kuhry, 2008). Kuhry (2008) suggest that landforms associated
with permafrost include palsa hummocks, peat plateaus and polygonal peat plateaus.
These landforms contribute to modifying the topography that may further influence soil
moisture by altering the local hydrology, water drainage pathways (Martini, 2006; Kuhry,
2008; Wang et al., 2009). Luoto & Seppälä (2002) suggests a complex spatial and
temporal interaction where palsas should mostly occur in areas that have undergone
periods of warm temperatures that provided significant soil moisture followed by
seasonal freezing. Kujala et al (2007) demonstrated that the thermal conductivity could
be enhanced with high moisture content (65%) for both frozen (1.5 Wkm-1
) and unfrozen
(0.5 Wkm-1
) soils when compared to low moisture content (56%) for frozen (0.6 Wkm-1
)
and unfrozen (0.2 Wkm-1
) soils. Since water has a higher energy transfer rate as solid ice
than in the liquid phase, the overall conductivity is greater at 1.5 Wkm-1
for frozen
compared to 0.5 Wkm-1
for unfrozen soils (Kujala, et al., 2007. The frozen peat layer acts
as an insulating layer during the next summer seasons to prevent thawing or heat
penetration promoting growth (Kujala, et al., 2007).
20
2.4.3 “Palsa Lifting”
Palsa growth in height is referred to as „lifting of the palsa‟ by Seppälä (1986) due
to the buoyancy properties of the ice core on wet peat where water is collected and stored
into the core, thus increasing its volume. The height of a palsa determines the extent in
which thawing can penetrate the mound. As freezing occurs downward, capillary water is
collected beneath the freezing layer, this process contributes to the formation of ice lenses
that segregate frozen peat layers (Brown, 1973; Seppälä, 1986; Kujala, et al., 2007;
Kuhry, 2008). The ice lens formation is also an extension of the permafrost, thus results
in the reduction of the base of the active layer. Experiments in man-made palsas by
Seppälä in 1982 illustrated this effect as frost was able to penetrate 70 cm downward into
the core of the palsas, and after two summers, 15-30 cm of the frost was still detectable in
October 1985 (Seppälä, 1986).
2.4.4 The Palsa Cycle
Seppälä (2003) noted the presence of Lycopodium annutinum, Huperzia selego,
Polytricum mosses and Cladonia lichens on newly developed palsas in the Finnish
Lapland. Depending on the region, palsa formation is observed in poorly drained areas
such as fens and bogs are dominated by Sphagnum species (Zoltai & Witt, 1995; Seppälä,
2003). Peat formation in bogs occurs over time as partial degradation of vegetation, such
as moss, into carbon organic matter (Zoltai & Witt, 1995). Seppälä (1986) suggests that
in order for palsa to begin the formation process, it would need a 50 cm thick insulating
layer of peat to develop first. The top layer cover then acts as an insulating layer and with
21
high moisture content, the thermal conductivity increases allowing deep frost penetration
(Seppälä, 1986).
The edges of the palsas are characterized as sharp steep edges that collect drifting
snow, however, since palsa freezing occurs from above towards the core, the edges
remain warmer and unfrozen (Seppälä, 1986). The collection of drifting snow by wind is
also a driver for palsa formation by acting as an insulating layer (Seppälä, 1986). Thin
layers of snow cover in the winter allow frost and cold to penetrate deeper into the peat
than with thick layers of snow. As the wind carries away the snow layer, the frost
penetration is enhanced, thus increasing the freezing of the peat. The growth of palsas is
not continuous, after a maximum height (about 7m to 12m), usually characterized by
formation of the sharp edges for snow drift collection and a top plateau, the frost layer
can no longer increase in thickness (Seppälä, 1986). In the summer, instead of snowdrift,
blowouts of sand dunes and glaciofluvial deposits of fine sands can become layered in the
palsa (Seppälä, 2003).
Seppälä (2003) acknowledged that blockside erosion due to rise in height allow
the formation of cracks. Enhanced by wind interactions, the edges of the palsas begin to
collapse, which signifies the degradation stages, and pools of water surrounding the palsa
form (Seppälä, 1986; Seppälä, 2003). Intense wind speeds above 50 m s-1
can enhance
erosion and degradation of the palsa (Seppälä, 1986; Seppälä, 2003). Internally, the ice
core may begin to melt causing an internal collapse of the palsa as a pond forms in its
place. The formation of a circular pit in the topography usually signifies a „dead‟ palsa
formation (Seppälä, 1986). However, this formation and degradation process was
suggested to be cyclic as new peat can develop in the ponds and pits created by remnant
22
palsas, and over time, provide the foundation for a new palsa core for development
(Seppälä, 1986). The degradation of a particular palsa may not necessarily be attributed
to climate change as suggested by Seppälä (1986) since the mechanism may be due to
this cyclic process over time.
2.5 Soil Temperatures and Net Radiation
A standard method for determining the presence of permafrost is to measure the
soil temperatures (Pilon et al., 1989; Mühll et al., 2002; Smith & Burgess, 2002; Kneisel
et al., 2008; Nicolsky, 2009). To measure soil temperatures, thermistors are deployed in
the active layer at set intervals (Pilon et al., 1989; Nicolsky, 2009). Thermistors are
defined as semi-conductor probes that measure electrical resistance in relation to
temperature (Pilon et al., 1989; Mühll et al., 2002; Nicolsky, 2009). Thermistors record
continuous time series of temperature data onto data loggers. The data loggers record and
allow the data to be downloaded later. Thermistors connected in series form a thermistor
cable (Pilon et al., 1989).
Surface temperature can be determined by using an infrared thermocouple sensor
or calculated by applying the Stefan-Boltzmann Equation:
εσTs4 = Qlw↑ + (1-ε)Qlw↓, (8)
where ε is the emissivity, σ is the Stefan-Boltzmann Constant (5.67x10-8
Wm-2
K-4
), Ts is
the surface temperature (Kelvin), Qlw↑ is the reflected longwave radiation (Wm-2
), Qlw↓ is
the sky longwave radiation (Wm-2
; Crepeau, 2006). Incoming and outgoing shortwave
and longwave radiations can be measured using a four-component radiometer (Hayashi et
al., 2007).
23
2.6 Ground Heat Flux
Halliwell & Rouse (1987) stated that buried soil heat flux plates are the standard
method in measuring ground heat flux. A soil heat flux plate is composed of a
thermopile, encased in an electrically insulating material that is placed between two
metallic plates (Halliwell & Rouse, 1987; Wen et al., 2008). When buried in the soil
layer, the heat flux passing through the plate results in a temperature difference across the
thermopile that is proportional to the flux density where a voltage output from the
thermopile can be measured and continuously recorded on data loggers (Halliwell &
Rouse, 1987).
Hayashi et al (2007) suggested that ground heat flux (Qg) for the energy balance
of the active layer consists of three components and can be calculated from the
calorimetric method:
Qg = Qi + Qs + Qp, in Watts per square metre (Wm-2
). (9)
Qi is the latent heat used to melt ice in the active layer represented by the
equation: Qi = ρƒLΔz, (10)
where ρ is density of ice (kgm-3
), ƒ is volumetric fraction of ice (unit less), L is the latent
heat of fusion (Jkg-1
), Δz is rate of frost table depth change (m).
Qs is the heat that warms the active layer represented by the equation:
Qs = Σi CidiΔTi, (11)
where „i‟ represents the location of soil thermistor of the thermistor cable, Ci is
volumetric heat capacity (MJm-3
ºC-1
), di is thickness (m), ΔTi is rate of daily
temperature change (ºC).
Finally, Qp is heat conducted into the permafrost layer from the upper active layer.
24
2.7 Geophysical Detection of Permafrost
With warming temperatures in polar regions, concerns of warming-induced
permafrost degradation, northern expansion of infrastructures, and the movement of
contaminants in the once frozen subsurface have driven the need for geophysical methods
to be applied in determining the extent of permafrost (Delaney et al., 2001; Tsuji et al.,
2001; Smith & Burgess, 2002; Sorochan & Tolmachev, 2006; Kalinovich et al., 2008;
Kneisel et al., 2008; Wang et al., 2009). Geophysical methods are applied to investigate
and characterize subsurface conditions over large areas. It should be noted that there is no
set standard geophysical method in determining permafrost (Pilon et al., 1989; Kurfurst,
1992; Hinkel et al., 2001; Nieto & Stewart, 2002; Smith & Burgess, 2002; Mühll et al.,
2002; Moorman et al., 2003; Kneisel et al., 2008). Kneisel et al. (2008) stated that most
geophysical methods for permafrost were derived from application of geophysical
methods from geological survey methods and petroleum exploration techniques since the
1970s. Certain methods have advantages in determining permafrost, such as detecting
boundary transitions, structures and sediment layers, but the same method will have
limitations, such as depth, resolution, misidentification of ice and rock, and the scale of
application. Since drilling borehole operations in permafrost is often expensive, time
consuming and logistically demanding, this is one of the main reasons in employing
geophysical methods (Tsuji et al., 2001; Mühll et al., 2002; Moorman et al., 2003; Saito
& Yoshikawa, 2007; Kneisel et al., 2008; Nicolsky, 2009).
25
2.7.1 Ground Temperature Borehole Logging
A classical method to determining the presence of permafrost is to measure the
ground temperatures (Pilon et al., 1989; Mühll et al., 2002; Smith & Burgess, 2002;
Kneisel et al., 2008; Nicolsky et al., 2009). To measure temperatures, thermistors are
deployed vertically in the subsurface usually in boreholes (Pilon et al., 1989; Kurfurst,
1992; Mühll et al., 2002; Nicolsky et al., 2009). Thermistors are semi-conductor probes
that measure electrical resistance in relation to temperature (Pilon et al., 1989; Mühll et
al., 2002; Nicolsky et al., 2009). Thermistors record continuous time series of
temperature data onto data loggers. The data loggers sort and allow the data to be
downloaded later. Thermistors can be connected in series to a Thermistor cable (Pilon et
al., 1989). Installation of thermistor cables occurs as an opportunistic operation following
excavation and borehole drilling operations (Mühll et al., 2002; Nicolsky et al., 2009).
This approach allows the collection of more data and reduces the expense in separate
borehole drillings (Mühll et al., 2002; Nicolsky et al., 2009). Permafrost is determined to
be present when ground temperatures are below 0ºC (Smith & Burgess, 2002). The
boreholes are typically encased using porous polyvinyl chloride (PVC) pipes where the
thermistor cable can be lowered into the subsurface (Kurfurst, 1992). However, the
protective PVC pipe can act as thermal contaminator and insulator that affects the
temperature measurements, this occurrence is referred to as “leaky cables” (Pilon et al.,
1989).
Borehole logging requires drilling into the subsurface (Saito & Yoshikawa, 2007;
Nicolsky et al., 2009). Three main types of drilling used in determining permafrost
depths are percussion, rotary and auger drillings. Percussion drilling requires the use of
26
heavy equipment and gasoline-powered machinery at the study site, and utilizes a weight
to create an impact force that bores through the subsurface material (Saito & Yoshikawa,
2007). Rotary drills utilize torque and axial forces with various drilling bits to create a
borehole that displace ground material by helical flighting along the axis of rotation of
the drill bit (Saito & Yoshikawa, 2007). Once the borehole is created, probes connected
to loggers by a wire are placed down the boreholes. However, not all boreholes can be
used due to the diameter of the hole, the presence of frozen fluids, and the stability of the
borehole walls (Saito & Yoshikawa, 2007). The presences of frozen fluids act as a barrier
against the probe from being lowered to the depth of the borehole. The stability of
borehole walls can be reinforced by inserting wall casings (Saito & Yoshikawa, 2007).
2.8 Literature Summary
Arctic soils are characterized by an upper organic layer, followed by an active
layer that varies in depth by season and underlain by permafrost that is ground material
frozen for at least two years (Waelbroeck, 1993; Gough & Leung, 2002). The high
moisture content of the peat and organic layer was determined to have a soil moisture
range of 16 to 65% by volume and indicated that the increase of moisture content allows
for greater dielectric conductance (Yoshikawa et al., 2004). Continuous permafrost is
present in climate favourable conditions and in regions dominated by a negative ground
heat energy balance. Gough & Leung (2002) determined inconsistencies with the Frost
number thresholds for characterizing permafrost presence along the western shores of
Hudson Bay and in Northern Ontario and suggested a greater role in the thermal
conductivity properties. Shur & Jorgenson (2007) suggested that freezing penetration
27
downwards into the active layer of the soil is enhanced by increased moisture content that
enhanced the thermal conductivity of energy transfer. Moisture content and insulation
provided by overlying vegetation and organic layers enhance the soil thermal
conductivity properties that allows for greater freezing penetration (Karunaratne and
Burn, 2004; Shur and Jorgenson, 2007; Wang et al., 2009). Removal of the vegetation
and organic layers reduces the insulation effect allowing for various degradation methods
of permafrost to occur (Karunaratne & Burn, 2004; Shur & Jorgenson, 2007; Zhang et
al., 2008b; Pang et al., 2009). Karunaratne & Burn (2004) and Shur & Jorgenson (2007)
suggested that the composition of the soil could determine the presence of permafrost, as
presence would be expected in regions of silty and clayey soils, and seldom in regions
with gravely soils due to the textures ability to retain moisture content. Soil moisture
content heavily influences the soil thermal conductivity that allows the conduction of the
thermal freezing and thawing energies into the soil column (Wang et al., 2009). A
thermal offset phenomenon favourable to permafrost presence occurs when freezing
energies in the winter season exceeds the summer thawing energy penetration, positive
heat flux, in the soil column resulting in a thickened frozen soil layer (Burns & Smith,
1987). Enhanced freezing can occur in highly saturated active layers above the
permafrost, the formation of palsas can result from the development of an ice lens that
cause a volumetric expansion of the soil to produce mounds (Brown, 1973; Seppälä,
1986; Kujala, et al., 2007; Kuhry, 2008). This cyclic process is influenced by vegetation,
atmospheric conditions, and soil thermal conductivity, that can be enhanced by the soil
moisture content, that enables downward freezing penetration into the soil, negative heat
flux (Seppälä, 1986; Kujala, et al., 2007). Hayashi et al (2007) suggested that the heat
28
and mass transfer equation can be coupled to simulate the thawing and freezing depths by
applying the Stefan equation based on the soil thermal conductivity, soil moisture content
and atmospheric forcing.
With northern climates predicted to continue on a warming trend, the increased
likelihood for environmental disturbances, such as permafrost and palsa degradation, are
expected and the changes will affect local wildlife and northern communities (Seppälä,
1986; Vyalov et al., 1993; Anisimov & Nelson, 1996; Sorochan & Tolmachev, 2006;
Kujala et al., 2007; Dyck et al., 2007; Callaghan, 2008; Crompton et al., 2008). Polar
bear (Ursus maritimus) habitats have been identified in Northern Ontario that is
dominated by permafrost and palsas (Callaghan, 2008; Crompton et al., 2008). In spring,
female polar bears display site fidelity behaviour by returning to dens that were
established in the previous year (Crompton et al., 2008). This site fidelity behaviour is
even prominent over feeding needs suggesting that shifts in permafrost may affect the
ecology of the region causing disturbances to the site fidelity behaviour, reducing the
survival fitness of cubs (Crompton et al., 2008; Dyck et al., 2008). Changes in the
ecology from shifts in permafrost may affect local food sources for polar bears affecting
the den locations and survival (Dyck et al., 2008).
Permafrost distribution and active layer monitoring involves high quality
atmospheric, soil, and hydrological data that can be collected using the standard borehole,
soil temperature and atmospheric measurements that can be complimented for larger
spatial scale with modern geophysical tools. Shifts in the permafrost will pose a greater
threat for engineering designs on infrastructures in aboriginal communities infrastructures
and for the industrial pipelines that traverse Canada‟s North. The phase change of water
29
to ice increases the soil strength by the process of cementation, however, the degradation
of permafrost can significantly weaken the strength of soil and reduce the load bearing
that can prove hazardous to human infrastructures and transportation networks (Christ &
Park, 2009). With warming temperatures and seasonal frost heaving processes, the
expansion and melting of the ice in frozen ground can result in both sudden and gradual
changes to infrastructure foundations that can compromise the structural stability and
safety of buildings (Ling & Zhang, 2004; Kim et al., 2008; Larsen et al., 2008; Christ &
Park, 2009; Duan & Naterer, 2009). Understanding and predicting the permafrost state is
important in engineering protocols in order to minimize risks to human safety and for the
environment (Vyalov et al., 1993; Sorochan & Tolmachev, 2006; Dyck et al., 2007;
Callaghan, 2008; Crompton et al., 2008; Kim et al., 2008; Larsen et al., 2008; Christ &
Park, 2009; Duan & Naterer, 2009).
30
CHAPTER 3: Experimental Design and Methodology
Two field-sampling campaigns were completed in mid-August of 2007 and 2008
along the shores of Hudson Bay and inland Northern Ontario. Gough and personnel from
the Ontario Ministry of Natural Resources conducted sampling and fieldwork. The study
area is located between 54º28.909 north to 56º47.759 north and from 83º36.585 west to
89º30.534 west from the shores of Hudson Bay to within 100 kilometres inland of
Northern Ontario (Figure 2).
Figure 2 – Location of settlements, weather stations and rivers in Northern Ontario. Map
produced with Manifold V.7 GIS software with UTM projection 16
31
3.1 Location and Study Site Descriptions
The communities of Peawanuck, Ontario, and Fort Severn 89, Ontario, are located
within the study area. The Indian Settlement of Peawanuck (55°00.500 N, 85°25.333 W)
is located in the Kenora District; governed by the Weenusk First Nation Band,
provincially by the Government of Ontario, and federally by the Government of Canada
(Figure 2). According to the 2001 Census conducted by Statistics Canada, the permanent
population count for Peawanuck is 193 (Statistics Canada, 2007). An updated count by
the Weenusk First Nation in 2007 showed a population of 300 (Weenusk First Nation,
2007a). The Peawanuck community is bilingual in Cree and English. Peawanuck is
bordered by Polar Bear Provincial Park and located near the Winisk River.
The First Nation Reserve of Fort Severn 89 (56°00.000 N, 87°21.000 W) is
located near the Severn River. Fort Severn is governed by the Cree First Nation,
provincially by the Government of Ontario, and federally by the Government of Canada
(Figure 2). The permanent population for Fort Severn is 639 as reported by the Indian and
Northern Affairs Canada registration (Indian and Northern Affairs Canada, 2008). Both
Fort Severn and Peawanuck are accessible by boat in the summer season and by air
service all year round. Ice roads connect the two First Nation communities during the
winter season.
It should be referenced that the ghost town of Winisk (55°15.402 N, 85°12.396
W), referred as Weenusk in Cree, Ontario, was the original Indian Settlement location
before the establishment of Peawanuck, Ontario (Figure 2). Winisk is located along the
Winisk River. The Winisk Flood of 1986 destroyed the settlement and resulted in the
relocation and establishment of Peawanuck, Ontario, about 35 kilometres to the south.
32
Winisk is a historical military radar site. The Royal Canadian Air Force (RCAF) Station
Winisk and airfield were established in the late 1950‟s as part of the Mid-Canada Line to
provide early warning radar detection against intercontinental ballistic missiles (Tsuji et
al., 2001). The Department of National Defence, in the mid-1960s, decommissioned the
station; however, there remain environmental concerns at this site (Tsuji et al., 2001).
3.1.1 Biogeography
The terrestrial ecozone for Fort Severn and Peawanuck, Ontario, is classified as
the Hudson Plains, located north of the Boreal Plains, in between the Taiga Shield, and
south of the Southern Arctic ecozone (Figure 3; Natural Resources Canada, 2007).
Figure 3 – Terrestrial Ecozones for the Hudson Bay Lowlands by Natural Resources
Canada (Natural Resources Canada, 2007)
33
Fort Severn and Peawanuck are dominated by subarctic vegetation that includes open
trees, shrubs, and wildflowers; this region is located in the Transitional Forest ecozone
and north of the Boreal Coniferous ecozone (Figure 4; Natural Resources Canada, 2003).
Figure 4 – Forested Ecozones for the Hudson Bay Lowlands by Natural Resources Canada
(Natural Resources Canada, 2003)
Peawanuck is located in the Hudson Bay Lowlands along the Winisk River,
where swamps, bogs and muskeg areas are found in adjacent wet areas (Figure 2). Fort
Severn is located to the west of Peawanuck near the mouth of the Severn River (Figure
2). The wildlife in the Fort Severn and Peawanuck regions are briefly listed as: Beaver,
Black Bear, Polar Bear, Caribou, Ermine, Arctic Fox, Red Fox, Snowshoe Hares, Lynx,
Moose, Otter, Mink, Muskrats, Snowy Owl, Crow and Wolf. Water Fowl included:
34
Canada Geese, Snow Geese, Swans, Sand Hill Crane, Loons and Ducks. Along the
Hudson Bay shores, it is typical to see: Walrus, Beluga Whales, and Seal (Weenusk First
Nation, 2007b). During the 2008 summer sampling campaign, the following were
observed in the study area: Caribou, Polar Bear, Eagle, Snow Geese, Loons, Whale, and
Sand Hill Crane.
3.1.2 Climate Data and Weather Stations
Weather stations located in the study area within the Hudson Bay watershed as
listed in use by Environment Canada Weather Office: Fort Severn (A) and Peawanuck
(AUT; Environment Canada, 2009a; Environment Canada, 2009b). Weather station
descriptions are shown in Table 1 and Figure 2.
Table 1 – Methodology: Environment Canada Weather Station Information with Climate, World
Meteorological Organization (WMO) and Transport Canada (TC) ID codes. (Environment Canada,
2009a; Environment Canada, 2009b)
Location Latitude Longitude Climate ID WMO ID TC ID
Fort Severn (A) 56°1.200' N 87°40.800' W 6012500 71099 YER
Peawanuck
(AUT)
54°58.800' N 85°25.800' W 6016295 71434 WWN
Average snow depths in centimetres, mean annual precipitation in millimetres,
soil and air temperatures in degrees Celsius, and permafrost zones were collected from
Environment Canada Weather Office stations in Peawanuck and Fort Severn, Ontario,
and from the Atlas of Canada of the Natural Resources of Canada, respectively
(Environment Canada, 2009a; Environment Canada, 2009b; Natural Resources Canada,
2006). Weather stations were installed in the 2008 summer campaign at the 2007
sampling-site of G5a/8E3 (Shagamu) (55°41.102 N, 86°51.325 W) and near 8A1 Burnt
Point (55°14.507 N, 84°19.032 W) by the Ontario Ministry of Natural Resources to
35
provide snow depth, air and soil temperature data and wind speed. This site is situated
between Fort Severn and Peawanuck, Ontario (Figure 2).
3.2 Field Experimental Design
3.2.1 Soil Temperatures and Thermistor Probes
Soil temperatures were determined using thermistor probes that were lowered into
a borehole created by the hand auger. The depths to the permafrost were measured by
using a graded rod. Permafrost presence was determined when soil temperature was at
freezing, 0ºC; the temperatures were recorded in the field notes.
3.2.2 Point-scale Geophysical Sampling
A total of 53 soil samples were collected in the two-year sampling campaign; 20
and 33 soil samples retrieved in August of 2007 and 2008, respectively (Figure 5). Within
the study area, observations were made at over 500 sites.
36
Figure 5 – Sampling Sites located in Northern Ontario Hudson Bay divided by Three Quadrants
from both 2007 and 2008 Soil Sampling Campaigns. Map produced with Manifold V.7 GIS
software with UTM projection 16
A hand auger was used to produce a borehole where soil samples from the surface, 30
and 120-centimeter depths were extracted and collected in plastic containers and double
plastic Ziploc bags (Table 2). Upon reaching the permafrost, the solid state of ground
prevented further auguring deeper into the subsurface, which can be confirmed by
lowering and striking a graded rod in the borehole. The soil samples were transported
back to the University of Toronto Scarborough campus. Helicopter support was used for
transportation to the sampling locations. The depths to the permafrost were determined
by lowering the graded rod into augured boreholes for measurements in centimetres.
Using Figure 2, the study area was divided into three quadrants (Figure 5).
Quadrant 1 included all the sampling sites in 2007 and 2008 that were located between
37
the provincial boundary line of Ontario and Manitoba and the western portion of the
Severn River (Figure 5; Tables 9 and 10). Quadrant 2 was divided to include all the
sampling sites in 2007 and 2008 that were located between the eastern portion of the
Severn River and the western portion of the Winisk Rivers (Figure 5; Tables 9 and 10).
Quadrant 3 included all the sampling sites in 2007 and 2008 that were located between
the eastern portion of the Winisk River and to the shores of James Bay (Figure 5; Tables
9 and 10). Figure 6 was produced to show the 2007 sampling campaign.
Figure 6 – Sampling Sites located in Northern Ontario - Hudson Bay for 2007 divided by Three
Quadrants. Map produced with Manifold V.7 GIS software with UTM projection 16
Figure 7 was produced to show the 2008 sampling campaign.
38
Figure 7 – Sampling Sites located in Northern Ontario - Hudson Bay for 2008 by Three
Quadrants. Map produced with Manifold V.7 GIS software with UTM projection 16
3.2.3 Sample Labelling and Identification
Each soil-sampling site from the study site was geo-referenced using a hand-held
global positioning satellite (GPS) system. Soil samples retrieved from the 2007 sampling
campaign were labelled with a unique identification key that corresponded with the
recorded field data in the field notes. For example, Sample “B1” represented a sample
from site „B‟ made on the „first‟ day of the campaign. This was conducted for all 20
samples in 2007. For the 2008 soil sampling campaign, the samples were labelled with a
second identification key that corresponded to the field notes. For example, Sample
“8A1”, „8‟ represents the „month of August‟ for sampling at site „A‟ on the „first‟ day.
This was conducted for all 33 samples in 2008 (Figure 8). The labelled soil samples, site
39
coordinates, temperature data, and the depths to permafrost measurements were recorded
in the field notes. Additional field data were recorded in picture documentation.
3.2.4 Field Soil Characterization
The soil properties in the field were characterized based on visual and physical
observations of colour, texture, and soil moisture that were recorded in the field notes.
The presence of organic areas, such as peat layers, bogs, fens, and the lack of organics
were noted in the field notes. Additional field data were recorded in picture
documentation. Soil samples were collected at the point-scale resolution into containers
and labelled appropriately before being transported to the University of Toronto
Scarborough campus for further in-depth analysis.
3.3 Laboratory Analytical Methodology
The soil samples retrieved from the 2007 sampling campaign were analyzed on October
4th
of 2007. The samples from the 2008 soil-sampling campaign were analyzed on
October 27th
of 2008. Both laboratory analyses were conducted at the University of
Toronto Scarborough campus. Laboratory methodology for soil moisture and acidity
analyses was adapted from the GLOBE (2005) protocol soil techniques.
3.3.1 List of Materials
The materials required for the soil sampling campaign and laboratory analysis in
2007 and 2008 are listed in Table 2.
40
Table 2 – Methodology List of Required Materials for Laboratory Analyses: 2007 & 2008 Sampling
Campaigns.
2007 Campaign 2008 Campaign
20 soil samples containers
20 200 ml Erlenmeyer beakers,
20 tin foil baking trays,
2 glass stir rods,
2 metal tablespoons,
2 Litres distilled water,
1 graduated 100mL cylinder
1 TDS pH meter,
1 25mL pH 7 buffer solution,
Baking oven, mass balance, and
paper towels.
80 Ziploc Bags
33 200 ml Erlenmeyer beakers,
33 tin foil trays,
2 glass stir rods,
2 metal tablespoons,
5 Litres distilled water,
1 graduated 100 mL cylinder
1 Symphony SB70P pH meter,
1 25 mL pH 7 buffer solution,
1 25 mL pH 10 buffer solution,
Baking oven, mass balance (Denver
Instrument MXX-2001), and paper towels
3.3.2 Laboratory Soil Characterization
In depth soil characterization of the retrieved soil samples were conducted at the
University of Toronto Scarborough campus soil laboratory. The labelled samples were
transferred from the sample containers into corresponding labelled tinfoil trays (Figure
8).
Figure 8 – Labeled sample bag with associated tin foil tray container: Sample
8A1a with sandy & rocky materials. Picture was taken on 4 OCT 08 by A. Tam
41
By using a glass stir rod, the sample could be dispersed (Figure 9).
Figure 9 – Analysis of soil sample D5a: Presence of fungus and partially
decomposing organic material. Picture was taken on 4 OCT 07 by A. Tam.
Observations were noted based on colour, texture, moisture content, the presence of
partially decomposed vegetation, presence of rocks and pebbles, aggregation, and any
unique characteristics such as fungus and moulds (Figure 9).
3.3.3 Gravimetric Soil Moisture Content
The gravimetric soil moisture content, θm, in percentage was determined using
the outlined principles and procedures outlined by Juma (2006), supported by the
GLOBE (2005) protocol. The mass of the tin trays, Tm, plastic sample container, Cm, and
bag, Bm, were determined and recorded using an electronic mass balance in units of
grams, g. The tinfoil trays containing the soil samples were placed onto a mass balance to
determine the Initial Total Mass, ITm. The initial total mass of the soil samples included
42
both the masses of the plastic sample container, Cm, and bag, Bm. To determine the soil
moisture mass, Wm, the mass of the plastic container and bag were subtracted from the
initial total mass (Equations 12 & 12a). In 2007 laboratory analysis, the Wm was
determined using the following equation:
(ITm) - [(Cm) + (Bm)] = (Wm). (12)
For the 2008 laboratory analysis, Equation 15 was modified to determine the Wm:
(ITm) - [(Bm)] = (Wm) (12a)
The tinfoil trays were then placed into the baking oven at the University of Toronto at
Scarborough Soil Lab at 105˚C for 24 hours (1 day) before being removed from the oven
(Figure 20), the tinfoil trays and soil samples were cooled down to ambient room
temperature (22°C) for 15 minutes, and the Final total mass, FTm, was recorded by the
mass balance.
To determine the mass of the oven-dried soil, ODSm, the final mass of the sample and
tray after drying, FTm, was subtracted by the mass of the tin tray, Tm:
(FTm) - (Tm) = (ODSm) (13)
To determine the soil moisture (Ws), the mass of the oven-dried soil was subtracted from
the soil moisture mass:
[(Wm) - (ODSm)] = (Ws) (14)
To determine the water content in percentage, θm, Ws was divided by Wm then multiplied
by 100:
(θm in %) = [(Ws) / (Wm)] * 100 (15)
This was repeated for all samples. The dried oven soil was collected back into the
containers for storage.
43
3.3.4 Soil Acidity, Average pH Value
To calibrate the pH probe, the probe tip was washed with distilled water and
immersed in a pH7 buffer solution for calibration as directed by the manufacturer‟s
specifications in calibration. To determine the acidity of the soil sample, 50 grams of
oven dried soil was measured and placed in a 200 ml Erlenmeyer beaker and 100 ml of
distilled water was added. The solution was manually stirred with a glass-stirring rod for
5 minutes before being left to settle for 15 minutes. After 15 minutes, the pH probe was
lowered into the solution for two minutes, and the pH value was recorded. Three trials
were conducted per each soil sample. The pH values were converted to the concentration
of Hydrogen, [H+]:
pH = -log[H+] , [H+] = [1/(10^pH)]. (16)
The arithmetic average of the concentration of Hydrogen of each 3 trials (Trial1,
Trial2, Trial3) per sample was calculated and recorded:
{[([H+] Trial1) + … + ([H+] Trial3)] / 3} = (mean [H+]). (17)
Finally, using Equation 16, the mean concentration of Hydrogen was converted back to
the mean pH value. This was repeated for all samples. The solutions were safely disposed
in the soil laboratory waste bins.
3.3.5 Soil Moisture Content Loss Test
A control test for water content loss by evaporation of the soil samples in the
plastic bag containment was conducted for 35 days (5 weeks) from March 4th
to April 8th
,
2008 using 9 control samples where plastic bags were filled with water and placed at
various locations around the University of Toronto Scarborough campus.
44
A mass water balance approach was applied for the soil moisture content control
test. The mass of the plastic containment bag, Mbag, was determined using an electronic
mass balance. Using a graduated 100 mL cylinder, 50 mL of ordinary water from the
laboratory was poured and sealed in the plastic bags then placed on the mass balance to
determine the total mass, Mbw. The mass of water, Mw, in grams was determined by the
equation:
[(Mbw) – (Mbag)] = (Mw). (18)
To convert Mw, in grams, to a volume in millilitres, Vw, the density of water at
23ºCelsius (0.9975 g/mL) can be used:
[(Mw) (g) / (0.9975 g/mL)] = (Vw). (19)
This process was repeated nine times for 9 control samples. The 9 control samples were
labelled with a unique identification key that corresponded with the laboratory notes. For
example, Sample “T1”, „T‟ represents the “Test” sample designation while „1‟ refers to
„Location #1‟. Initial leak test of the test samples were conducted and recorded to
determine if the containment was compromised. Three test samples had one-level of
containment, a seal single layer plastic bag with 50 mL of water. The next three test
samples had a two-level containment, a sealed single plastic bag with 50 mL of water
within a sealed outer plastic bag. The last three test samples were given three-level
containment, a sealed single plastic bag with 50 mL of water within a sealed inner plastic
bag sealed in an outer plastic bag. One test sample of each level of containment was
placed around the University of Toronto Scarborough campus for 5 weeks. Test samples
T1, T4 and T5 were placed in the University of Toronto Scarborough campus soil
laboratory, Science Wing Room 313, to simulate water loss over the given period. Test
45
samples T2, T6 and T9 were placed in Science Wing Room 653, to simulate water loss
over the given period in a faculty office setting. Test samples T3, T7 and T8 were placed
in University of Toronto Scarborough Foley Hall Residence, to simulate water loss over
the given period in a storage setting. After the 5 weeks, the mass of the test samples,
M5wks, were determined using the electronic mass balance.
The change in mass water, ΔMw, difference could be calculated from:
[(M5wks)-(Mbw)] = (ΔMw), (20)
To convert the change in mass water, in grams, to a volume loss, Vloss, in millilitres, the
density of water at 23ºCelsius (0.9975 g/mL) can be used:
[(ΔMw) (g)/ (0.9975 g/mL)] = (Vloss). (21)
To finally determine the percentage of water lost, WL%, after five weeks, the following
can be applied:
[(Vloss)/(Vw)]*100 = (WL%). (22)
3.4 Stefan Depths and Permafrost Table Calculations
The Stefan depths were determined using Equation 3. The depth to permafrost, d,
were extracted from field notes and data provided by Gough. Average depths to
permafrost were calculated using the collected field data on permafrost depth with an
arithmetic average approach. When the calculated seasonal Stefan depth of freezing
exceeds the seasonal Stefan depth of thawing (Du < Df), the resulting positive thermal
offset represents the theoretical thickness of a frozen layer of soil that has persisted over
the summer thawing season, and has survived into the next freezing cycle (Burns &
46
Smith, 1987; Duan & Naterer, 2009). When the thermal offset conditions of Df < Du,
there is a loss of frozen ground at the frost table (Burns & Smith, 1987).
3.5 Thawing and Freezing Degree-Days Calculations
Thawing and freezing degree-days (TDD, FDD, respectively) were calculated
using temperature data collected from the weather station in Peawanuck, Ontario. The
temperature data prior to 1986 were collected from the Winisk, Ontario weather station.
Following the destruction of Winisk and the relocation of the community to Peawanuck
in 1986, all temperature data after 1986 were obtained from the present day weather
station Peawanuck (AUT). In calculating thawing degree-days, the cumulative number of
days above 0ºC was counted for a single year record. For the freezing degree-days, the
cumulative count of the number of days below 0ºC was counted for a single year interval.
For a one-year interval, this calculation requires 12 months of temperature data. Twelve
month was chosen from the beginning of July from the previous year to the end of June
of the next year. A thawing degree-day calculation example for the year of 1992 would
be to count the number of days above 0ºC starting from July 1st of 1991 ending on June
30th
of 1992 and then determine the sum of the number of count of days above 0ºC. This
was repeated for calculating freezing degree-days.
47
3.6 Geographical Information Systems
Geographical Information Systems (GIS) was used to produce a geographical map
of the sampling area based on degree-decimal location coordinates. The location
coordinated were geo-reference using hand held Global Positioning Satellite (GPS)
device conducted by personnel from the Ontario Ministry of Natural Resources. A map of
the Hudson Bay region was also produced in GIS Manifold System software version 8
and drawings from ESRI Data and Maps Volume One. The Universal Transverse
Mercator (UTM) coordinate system was applied as the map projection. UTM zones 16
and 17 were utilized for the GIS map projection. GIS was used to extract distances from
the sample sites to the nearest shore of Hudson Bay using the query function and the
software reported distances in units of metres.
48
CHAPTER 4: Results
4.1 Climate and Environmental Data
Both climate and environmental data were collected for the Fort Severn and
Peawanuck, Ontario, sites. The mean annual precipitation for the Hudson Bay lowlands
was determined to range from 401 to 600 millimeters (Natural Resources Canada, 2006).
The mean maximum snow depth in the Hudson Bay lowlands was determined to range
from 30-49 centimetres (Natural Resources Canada, 2006). The subsurface stratigraphy
of Fort Severn and Peawanuck is continuous permafrost (Figure 10; Natural Resources
Canada, 2006).
Figure 10 – Subsurface stratigraphy classification of Northern Ontario and Hudson
Bay by Natural Resources Canada (Natural Resources Canada, 2006)
49
A summary of the minimum and maximum winter (January) and summer (July) daily
temperatures for Fort Severn and Peawanuck are shown in Table 3.
Table 3 – Results: Elevation and Annual Temperature Ranges in Northern Ontario communities
from Environment Canada. (Environment Canada, 2009a; Environment Canada, 2009b).
Location Relief
Elevation
(metre)
Minimum
Daily
January
Temperature
– Winter
(ºC)
Maximum
January
Daily
Temperature
– Winter (ºC)
Minimum
Daily July
Temperature
– Summer
(ºC)
Maximum
Daily July
Temperat
ure –
Summer
(ºC)
Fort Severn 15.80 m -34 to -30 -24 to -20 6 to 10 16 to 20
Peawanuck 52.70 m -29 to -25 -24 to -20 6 to 10 16 to 20
4.2 Soil Characterization (2007-2008)
Using GIS software and GPS coordinates for the sample sites recorded in the field
notes, Figures 5 to 7 were produced to include sample site locations from the shore of
Hudson Bay to approximately 100 kilometers inland.
Soil characteristics of the retrieved soil samples and over 500 site observations
revealed soils of the Cryosols and Histosols orders which typically have permafrost
presence within the first two-metres in depth (Juma, 2006). Site descriptions from the
field notes revealed extensive peat formations and organic matter content in the poorly
drained soils. Further laboratory analyses of the soil samples are shown in Table 6.
Distances from the sampled sites to the nearest shore of Hudson Bay were extracted to
Tables 4 and 5. The results of soil characterizations from August 2007 and 2008 are
shown in Tables 4 and 5, respectively. There were 20 sites and soil characterizations for
2007 and 33 for 2008 totaling 53 characterizations during the two-year sampling
campaign (Tables 4 and 5).
50
Table 4 – Results: Site & Soil Characterizations from 2007 Soil Sampling Campaign with Distances
from the Shores of Hudson Bay to the Sample Sites.
Sample
ID Latitude Longitude
Distance to
Hudson Bay
(m) Site & Soil Characteristics
B1 55°15.405 -85°12.394 10000
Site was heavily vegetated. Soil sample was
aggregated with the presence of organic
matter (woody stems, roots and moss).
Sample appeared light brown/gray colour
and a gritty clay texture. No detectable
odour.
B2 55°20.032 -85°27.129 9341
Situated in grassy vegetation. Some
aggregation present in soil sample. Presence
of organic matter (fine roots). Sample
appeared light brown in colour, clayey
texture with moderate moisture. Gravel was
present at 100 cm depth. No detectable
odour.
B3 55°20.032 -85°25.673 8134
Soil sample was not well aggregated.
Presence of organic matter (fine roots) with
high moisture content. Soil appeared dark-
brown colour. Presence of gravel. Strong
musky odour.
B4 55°11.745 -85°39.212 29136
Sample site located on a palsa. Hummocky
Tundra terrain with the presence of a "baby
palsa." Presence of organic matter (partial
decaying grasses and fibrous roots). Soil
sample was well aggregated and dry. No
detectable odour.
B5 55°02.865 -85°51.121 49826
Presence of organic matter (twigs). Mostly
decomposing plant organic material. Soil
appeared dark and very moist. No
detectable odour. Soil contained presence of
three miniscule worm-like organisms.
B6 54°56.772 -86°06.884 69600
Site was situated on a palsa adjacent to a
pond. Other ponds were observed in the
area. Sample was well aggregated with high
organic matter content. Soil sample had
presence of organic matter (fine roots). No
detectable odour.
51
C2c 55°04.860 -84°15.321 21258
Site was located in a vegetated fen near a
palsa (15-20 metres wide). A dried mudflat
south of the palsa was observed adjacent to
the sampling site. An area with trees is
located 20 metres to the north of the palsa.
Presence of organic matter (decomposing
leaves, stems, and pod husks). Husks
appeared white internally and dark brown
externally. Soil colour appeared dark brown
with organic matter and very moist
conditions. Presence of fine sediments. No
detectable odour.
C3 54°54.146 -84°10.322 41836
Sample site was located on a steep terrain
adjacent to a palsa and ponds with adjacent
trees. Soil colour appeared light brown.
Presence of organic matter (peat, fungus,
molds, and roots). The soil sample was dry.
No detectable odour.
C8 55°16.289 -83°50.593 500
Sample site was located on the coast of
Hudson Bay in a fen at the north aspect of a
coastal ridge. Willows were observed at the
site. There was presence of organic matter
(moss and fibrous roots with a spongy
texture). Sample appeared dark brown in
colour and dry. Presence of fine particulate
matter with weathered and rounded pebbles
that appeared white & black. Gravel was
observed at a depth of 10 cm. No detectable
odour.
D1 54°56.873 -83°46.804 31719
Sample site was located at the centre of a
palsa plateau. Adjacent area to the east was
relatively treeless. Palsa fens are located to
the south, west and north of the sample site.
Palsa centre was 90 cm in height. A new
palsa formation was observed (3 m wide by
20 m long) and dark in appearance to the
north. Presence of organic matter (dense
fibrous roots, decaying leaves, fungus, moss
and mold). Sample had a clayey texture. No
detectable odour
52
D2 55°06.382 -83°48.716 15233
Sample site was located at the centre of a
palsa surrounded by a moat. Standing water
was present to the east, west and northern
edges. Soil samples showed presence of
organic matter (woody stems, roots, leaf
litter, and dark-brown coloured peat).
Moderate moisture content. No detectable
odour.
D4l 55°00.503 -83°12.043 21606
Sample site was located 3 m into a fen. Soil
sample showed presence of organic matter
(fibrous roots, decaying plant matter, leaf
litter, and fungus with a spongy texture).
The sample was moist. No detectable odour.
D5a 54°50.442 -83°03.364 31420
Sample site was located on a coastal plain
with the presence of trees. Samples were
retrieved from a central palsa. Presence of
organic matter (white moss, fungi, partial
decaying grass, twigs, woody stems, and
roots). The sample appeared light brown in
colour. There was presence of weathered
and rounded pebbles. No detectable odour.
E1 56°21.871 -89°30.534 64315
Sample site was located at the centre of a
palsa. Standing water was observed to the
northern edge of the palsa. A 1-metre
depression with standing water in the palsa
was speculated as a thaw slump. Presence
of organic matter (long fibrous roots, plant
stems, peat and decomposing organic
matter). No detectable odour.
E2 56°30.401 -89°18.550 44307
Sample site was located 25 m in a fen and
on a 0.5 m tall palsa. Presence of organic
matter (decaying bark and twigs). Soil
sample appeared to have a sandy and grainy
texture that had a light reddish-orange
colour. No detectable odour.
E2a 56°30.401 -89°18.550 44307
Sample site was located 1 m from the
southern edge of a fen. Presence of organic
matter (roots, grasses, decaying bark, leaves
and twigs). Soil sample appeared light
brown in colour. No detectable odour.
53
E6 56°26.585 -88°36.857 21074
Sample site was located in hummocky
lichen woodland with a large palsa plateau.
Forested area was well developed. Presence
of soil organic matter (roots, stems, and
peat). Presence of weathered and rounded
black pebbles. The soil appeared light
brownish-yellow colour with an orange
horizon. The soil had a sandy texture. No
detectable odour.
E10 56°22.395 -87°54.609 500
Sample site was located in a dried fen with
gravel edges. Samples were taken 2.5, 5 and
10 metres into the fen. Soil samples showed
presence of organic matter (dense root
networks with a spongy characteristic,
grasses, leaves, and woody stems). Soil had
an overall dark-brown colour. Sample had a
presence of fine sediments. Clayey soil was
observed in the sample site. Strong foul
odour was present.
F8 55°13.126 -84°41.726 2046
Sample site was located 2 km from the
Hudson Bay coast on a beach ridge.
Presence of organic matter (decaying thick
root systems). Sample contained rocks and
pebbles. Soil colour appeared to have a
mixture of dark & light shades of brown.
Sample was dry and had a sandy texture.
No detectable odour.
G5a 55°41.102 -86°51.325 21289
The sample site was in a fen field at the
centre of an emerging palsa. Soil sample
contained presence of organic matter (dense
roots, white mold, decaying twigs and
grasses). Soil was primarily organic matter.
No detectable odour.
Table 5 – Results: Site & Soil Characterizations from 2008 Soil Sampling Campaign with Distances
from the Shores of Hudson Bay to the Sample Sites.
Sample
ID Latitude Longitude Location
Distance to
Coast (m) Soil & Site Characteristics
8A1 55°14.507 -84°19.002 Coastal 2842
Sampling at Burnt Point near a
fence post in a fen. Presence of
sand with round weathered
gravel. Gravel had white and
black colours. No organic matter
content was observed. Sandy and
silty soil texture. No detectable
54
odour. Whales were observed in
Hudson Bay from this location.
8A2 55°36.618 -85°48.648 Coastal 367
Sample site was located to the
north of a grass area on a beach
ridge near a fen along the coast.
Site had high moisture content.
Sandy and clayey soils were
observed with weathered pebbles.
No organic matter content was
observed. No detectable odour.
8A3 55°27.630 -85°58.379 Inland 19329
Sample site was dominated by a
hummocky palsa with an
emerging palsa to the west. Peat
and moss were observed at the
site. No detectable odour.
8B1 55°28.982 -85°59.529 Inland 18421
Sample site was located on a
beach ridge. High soil moisture
content. Gravelly soil texture.
Rounded and weathered gravel
stones with black and white
colours. No organic matter
content was observed. No
detectable odour. A polar bear
was observed.
8B2 55°52.162 -86°47.037 Coastal 90
Sample site was located on a
beach ridge near the coast. Site
had high moisture content. Sandy
soil was observed in the upper 10
cm with weathered pebbles.
Gravelly soil was observed at a
depth of 2 m. No organic matter
content was observed. No
detectable odour.
8B3 55°55.436 -87°11.034 Coastal 940
Sample site was located on a
beach ridge near the coast and a
fen. Sandy and clayey soil
textures were noted. Site had high
moisture content. No organic
matter content was observed. No
detectable odour.
55
8B4 56°22.281 -87°54.601 Coastal 500
Adjacent to 2007 site “E10”.
Sample site was located on a
beach ridge and near a fen. A few
trees were noted in the area. Soil
from the beach ridge was sandy
and gravelly with weathered
pebbles. Soil from the beach ridge
had high soil moisture content.
Soil from the fen was dominantly
clayey. Whales and a mink were
observed in the area. No
detectable odour.
8C1 55°16.296 -83°50.592 Coastal 655
Adjacent to 2007 site “C8”.
Sample site was located on a
beach ridge near the south of a
fen. High soil moisture content.
Soil in the beach ridge had a
gravelly soil texture. Soil in the
fen was dominantly clayey. No
detectable odour.
8C2 55°11.730 -83°17.420 Coastal 1468
The site had shrub vegetation
without any tall trees and located
on a beach ridge. Site had high
moisture content with ponds and
large puddles. Clay soil was
detected under an upper peat
layer. Below the clay soil, sandy
soil was observed. No detectable
odour. A Greater Yellow Leg was
observed in the area.
8C3 55°12.499 -82°57.808 Coastal 1339
Sample site was located on a
beach ridge dominated with
grasses and shrubs. No trees were
in the area. Surface soils had a
gravelly and sandy texture with
black and white pebbles. Site had
high soil moisture content. No
detectable odour.
8C4 55°02.715 -82°51.658 Coastal 8765
Site was located on a beach ridge
dominated by gravelly and sandy
soils. No presence of organic
matter. Site had high soil
moisture content. No odour
detected.
8C5 54°48.174 -82°12.008 Coastal 85
Site was located at the shores of
James Bay on sandy dunes and
56
beach known as Hook Point. Site
was moderately vegetated
dominated in sandy soils. Site had
high soil moisture content. No
detectable odour.
8D1 55°43.908 -86°29.256 Coastal 6388
Site was located on a beach ridge
near a palsa and fen. The surface
was dominated in peat.
Weathered and rounded gravel
were observed at the surface. Soil
below the gravel was clayey. Site
had high soil moisture content.
No detectable odour. An eagle
nest was observed in the area.
8D2 56°25.104 -88°09.957 Coastal 7631
Site was located on a beach ridge
near a fen. Trees were observed in
the fen. Surface soil was
dominantly sandy and clayey.
Wet gravel was observed at
greater depths.
8D3 56°35.560 -88°25.510 Coastal 560
Sample site was located on a
beach ridge near a fen. Clayey
and sandy soils were observed
near the fen with pebbles. No
detectable odour.
8D4 56°47.266 -88°57.621 Coastal 5680
Site was located on a beach ridge
dominated by sandy and clayey
soils. Site had high soil moisture
content. No detectable odour.
8D5 56°26.550 -88°36.048 Inland 21074
Adjacent to 2007 site “E6”. Site
was located in lichen woodland.
8E1 55°37.780 -87°33.988 Inland 37800
Site was located on a palsa
plateau dominated in peat. Some
trees were observed in the area
and remnants of a fen. The site
had high soil moisture content
with the presence of bogs. Clayey
soil was observed below the peat
layer. No detectable odour.
8E2 55°31.322 -86°58.361 Inland 39841
Site was located in lichen
woodland with a pond to the
southwest. Low trees and shrubs
were observed in the area. Site
had high moisture content. No
detectable odour.
8E3 55°41.111 -86°51.326 Inland 21289 Adjacent to 2007 site “G5a”. Site
57
was located on a palsa with an
emerging palsa nearby and
surrounded by a fen. The site has
low vegetations and no trees. Site
had high soil moisture content.
Nearby fuel barrel cache was
damaged due to vandalism.
8E4 55°15.623 -85°12.639 Coastal 50
Site was located near Winisk,
Ontario, near the coast. Site was
well vegetated by grass. Surface
soil layer was dominated by
organic material underlain by
clay. No detectable odour.
8F1 55°46.94 -87°22.559 Inland 17663
Site was located in a fen
dominated by lichen. Presence of
an old palsa was observed. Soil
had high moisture content.
8F2 55°30.075 -86°36.199 Inland 30768
Site located in lichen wooden.
Site was observed to have been a
burned area with some surviving
trees. Gravel was observed at a
depth of 45 cm.
8G1 55°13.124 -84°41.727 Coastal 2040
Adjacent to 2007 site “F8”. Site
was located on a beach ridge
dominated by sandy and clayey
soils. Gravelly soils were
observed below the surface layer.
Site had high soil moisture
content. No detectable odour.
8G2 55°02.797 -83°06.238 Inland 12407
Site was located in a shallow
Polar Bear den on a ridge of
hummocky organic material.
Sedges and low growth vegetable
was observed in the area.
8G3 55°02.541 -83°04.724 Inland 11151
Site was located in a Polar Bear
den and 20 metres from a beach
ridge and fen. Sandy soil was
observed at the site. Standing
water was observed at the fen. A
Boreal Chorus Frog (Pseudacris
maculata) was identified at the
site.
8G4 54°38.784 -83°03.361 Inland 53321
Hummocky surface soil was
dominated by sphagnum. Clayey
soil was observed below the
organic layer. Soil had high
58
moisture content.
8H1 54°42.897 -84°06.587 Inland 58298
Site was located in lichen
woodland on a ridge. Clayey soil
was observed at the site. Bird nest
was observed to the south of the
ridge. Polar Bear tracks and a
hole possibly excavated by a
Polar Bear were observed. Soil
had moderate moisture content.
4.3 Laboratory Analysis Results (2007-2008)
4.3.1 Soil Moisture Content and Soil Acidity
The results from the laboratory analysis work were completed on October 4th
of
2007 for the gravimetric soil moisture content and soil acidity from the samples retrieved
from Northern Ontario and Hudson Bay (Figure 6). The gravimetric soil moisture content
and soil acidity results are summarized in Table 6.
Table 6 – Results: 2007 Laboratory Analysis for Gravimetric Soil Moisture Content and Acidity for
Northern Ontario
Results: Northern Ontario - August 2007
Sample
Identification
Gravimetric
Soil Moisture
Content Soil Acidity
SID θm (%) pH Average
B1 31.9 7.09
B2 63.2 6.90
B3 93.9 6.02
B4 72.0 5.75
B5 94.0 5.95
B6 73.2 3.71
C2c 92.7 5.40
C3 71.9 4.16
C8 22.9 6.06
D1 81.6 4.24
D2 78.8 4.75
D4l 92.5 6.06
D5a 81.1 3.99
E1 31.1 3.50
59
E10 94.2 6.06
E2 10.2 6.84
E2a 56.1 5.47
E6 5.6 5.79
F8 28.6 5.79
G5a 76.9 5.34
The majority of the samples was composed of organic material such as peat or
soils with fibrous roots and partially decomposed moss. The overall results showed high
soil moisture condition in which eighteen (18) of the twenty (20) samples had gravimetric
soil moisture content, θm, greater than 20% (Table 6). Fourteen (14) of the 20 samples
had gravimetric soil moisture content, θm, greater than 50% soil moisture content (Table
6). The samples were acidic overall with a mean pH of 4.41 (STD = 1.06; Table 6).
Average pH was calculated using the methodology outlined in 3.3.4 Soil Acidity,
Average pH Value.
The samples from the 2008 soil-sampling campaign were analyzed on October
27th
of 2008 for the gravimetric soil moisture content and soil acidity from the samples
retrieved from Northern Ontario and Hudson Bay (Tables 7 & 8). The analysis and
results were divided based on coastal and inland regions of the sample area (Figure 7).
The results are shown in Tables 7 & 8.
The results from the analysis of the twenty-three (23) coastal samples along
Hudson Bay showed drier gravimetric soil moisture, θm, conditions in which twenty-two
(22) of the 23 samples were less than 30% soil moisture content (Table 7). Fourteen (14)
of the 23 samples had soil moisture contents greater than 10% soil moisture content and
only three (3) of the 23 samples had soil moisture contents greater than 20% soil moisture
content (Table 7). The highest coastal soil moisture content was 37.5% at site 8C2 in
60
2008 (Table 7). The mean pH for the coastal samples was 7.14, slightly basic (STD =
0.05; Table 7).
Table 7 – Results: 2008 Laboratory Analysis for Gravimetric Soil Moisture Content and Acidity for
Sampling Sites along the Shores of Hudson Bay.
Results: Shores of Hudson Bay - August
2008
Sample
Identification
Gravimetric
Soil Moisture
Content Soil Acidity
SID θm (%) pH Average
8A1 15 7.1 7.11
8A1 30 5.7 7.10
8A1 65 5.5 7.15
8A1 120 14.2 7.14
8A2 9.3 7.12
8A2 18 25.7 7.18
8B1 6.6 7.17
8B2 8.6 7.07
8B3 12.6 7.13
8B4 10 10.0 7.17
8B4 PF 15.6 7.18
8C1 12.6 7.08
8C2 37.5 7.09
8C3 9.7 7.09
8C4 10.1 7.08
8C4 137 15.4 7.18
8C5 7.6 7.33
8D2 15.9 7.12
8D3 10.8 7.08
8D4 20.1 7.17
8G1 0 9.4 7.15
8G1 116 16.4 7.15
8G1 PF 14.9 7.17
Results from the analysis of the ten (10) inland soil samples from Northern
Ontario showed higher soil moisture content, θm, conditions in which six (6) of the 10
soil samples were greater than 20% soil moisture content and only two (2) of 10 samples
with less than 15% soil moisture content (Table 8).
61
Table 8 – Results: 2008 Laboratory Analysis for Gravimetric Soil Moisture Content and Acidity for
Sampling Sites inland in Northern Ontario.
Results: Inland Northern Ontario - August
2008
Sample
Identification
Gravimetric
Soil Moisture
Content Soil Acidity
SID θm (%) pH Average
8D5 6.5 7.02
8E1d 21.5 7.39
8E2a 91.0 6.00
8F1a 92.1 6.76
8F2a 12.5 7.14
8F4a 47.4 7.09
8G4a160 19.4 7.50
8G4asfc 95.4 5.37
8H1a10 77.1 6.00
8H1a100 18.5 7.48
The mean pH for the inland samples was 6.17, therefore slightly acidic (Table 8). The
highest inland soil moisture content value was 95.4% at site 8G4 in 2008 (Table 8).
4.3.2 Measured Depths to Permafrost
Point-scale depths to permafrost were measured at twenty (20) sites along the
shores of Hudson Bay and inland in Northern Ontario using a graded rod (Figure 6). This
was conducted in August of 2007; the results for the depths to permafrost and the
location of each sample site in the designated quadrants are shown in Table 9.
62
Table 9 – Results: Depths to Permafrost for 2007 Sampling Site and Classified by Quadrants
Sample
ID
Average
Depths to
Permafrost
(cm) Quadrant on Map
B1 68 2
B2 N/A 2
B3 N/A 2
B4 35 2
B5 N/A 2
B6 37.5 2
C2c 39 3
C3 47 3
C8 10 3
D1 52 3
D2 42 3
D4l 86 3
D5a 37 3
E1 49 1
E10 58 1
E2 33 1
E2a 40 1
E6 N/A 1
F8 52 3
G5a 48 2
In August of 2008, point-scale depths to permafrost were measured at twenty-eight (28)
sites along the shores of Hudson Bay and inland in Northern Ontario using a graded rod
(Figure 7). Depth to permafrost was confirmed using a thermistor probe to determine the
minimum and mean soil temperatures. The results of the mean depths to permafrost, soil
temperatures and the location of each sample site in the designated quadrants are shown
in Table 10.
63
Table 10 – Results: Depths to Permafrost for 2008 Sampling Site and Classified by Quadrants
Sample
ID
Average Site Depth to
permafrost (cm)
Average Site
Soil
Temperature
(ºC)
Site Soil
Temperature
(min ºC)
Quadrant
on Map
8A1 119.67 5.27 1.82 3
8A2 125.5 3.56 1.58 2
8A3 48.17 1.1 0.14 2
8B1 108 1.9 1.9 2
8B2 85 1.83 1.58 2
8B3 114.5 0.9 0.9 2
8B4 96.25 1.47 1.47 1
8C1 110.75 2.07 1.26 3
8C2 95 8.2 8.2 3
8C3 93 5.58 4.96 3
8C4 99 4.31 3.19 3
8C5 182 1.77 1.77 3
8D1 39 0 0 2
8D2 149.5 3.98 2.01 1
8D3 99 0.46 0 1
8D4 142 0.09 0.09 1
8D5 175 10.5 10.5 1
8E1 140.8 1.11 0.29 2
8E2 256 2.6 2.6 2
8E3 83.82 0.96 0.18 2
8E4 193.5 5.38 5.17 2
8F1 145.67 6.6 4.86 2
8F2 175 10.87 10.87 2
8G1 140.5 0.72 0.48 3
8G2 49.89 0.65 0.23 3
8G3 53.71 2.87 0.87 3
8G4 147.67 2.62 2.36 3
8H1 166 2.96 2.39 3
The mean depths to permafrost were calculated from Tables 9 & 10 according to the map
quadrants where each site was located and the results are shown in Table 11.
64
Table 11 – Results: Yearly Average Depths to Permafrost per Quadrant
Average Depths to Permafrost (cm)
Year Quadrant on Map
--- 1 2 3
2007 45.0 47.13 45.63
2008 132.35 126.25 114.29
4.4 Freezing and Thawing Degree-Days (1989-2007)
4.4.1 Results from 1989 to 2002
The freezing and thawing degree-days from 1989 to 2002 were calculated from
temperature data collected from the northern community weather station at Peawanuck,
Ontario. The results are shown in Figures 11 and 12 and the statistical data were shown in
Tables 12 and 13.
Results: Peawanuck Degree Days (1989 - 2002)
0
200
400
600
800
1000
1200
1400
1600
1800
2000
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Year
Degre
e D
ays
Thawing Degree Days Freezing Degree Days
Figure 11 – Results: Freezing and thawing degree-days for Peawanuck, Ontario, from 1989-2002
65
The thawing degree-days appear to have generally increased between the years of
1989 to 2002 with slight decreases in 1992, 1995, 2000 and 2002; test of significance
using regression analysis with a 95% confidence interval was performed, and the p-value
of 0.106 suggests that the observed trend is not statistically significant (R2 = 0.216; r =
0.465; Figure 11; Table 12).
Table 12 – Results: Statistical Analysis of the 1989 – 2002 Peawanuck Degree-Days
Peawanuck Degree Days
1989 - 2002
Thawing
Degree Days
Freezing
Degree Days
STD 164 297
MEAN 1433 1192
R2 0.216 0.660
p-value
(95% CI) 0.106 0.000
The peak thawing degree occurred in 2001 at 1798 thawing degree-days. The freezing
degree-days appear to have generally decreased between the years of 1989 to 2002; test
of significance using regression analysis with a 95% confidence interval was performed,
and the p-value of 0.000 suggests that the observed trend is statistically significant (R2 =
0.660, r = -0.812; Figure 11; Table 12). From 1989 to 2000, the number of freezing
degree days decreased from 1614 to 557 freezing degree-days (Figure 11). There was an
increase in freezing degree-day from 2000 to 2001, 557 to 1105 freezing degree-days
respectively (Figure 11). As shown in Figure 11, the number of freezing degree days per
year in the late 1980s and early 1990s exceeded the number of thawing degree-days for
the same year. From 1993 onwards, the thawing degree-days per year exceed the freezing
degree-days per year. As the thawing degree-days in Peawanuck increased, there was a
decrease in the freezing degree-days.
66
4.4.2 Results from 2004 to 2007
The freezing and thawing degree-days from 2004 to 2007 were calculated from
temperature data collected from the Peawanuck weather station (Figure 12).
Results: Peawanuck Degree Days (2004 - 2007)
1025
1751 17181659
1054
1439
722
1232
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2004 2005 2006 2007
Year
Deg
ree D
ays
Thawing Degree Days Freezing Degree Days
Figure 12 – Results: Freezing and thawing degree-days for Peawanuck, Ontario, from 2004-2007
The thawing degree-days appear to have generally increased between the years of
2004 (1025 thawing degree days) to 2007 (1659 thawing degree days) with a peak
increase in 2005 at 1751 thawing degree-days; test of significance using regression
analysis with a 95% confidence interval was performed, and the p-value of 0.301
suggests that the observed trend is not statistically significant (R2 = 0.491; r = 0.701;
Figure 12; Table 13).
67
Table 13 – Results: Statistical Analysis of the 2004 - 2007 Peawanuck Degree-Days
Peawanuck Degree Days
2004 - 2007
Thawing
Degree Days
Freezing
Degree Days
STD 345 303
MEAN 1538 1112
R2 0.491 0.006
p-value
(95% CI) 0.301 0.920
The freezing degree-days appear to have slightly increased between the years of
2004 (1054 freezing degree day) to 2007 (1232 freezing degree days) with a peak
decrease in 2006 at 722 freezing degree-days; test of significance using regression
analysis with a 95% confidence interval was performed, and the p-value of 0.920
suggests that the observed trend is not statistically significant (R2 = 0.006, r = 0.077;
Figure 12; Table 13). As shown in Figure 12, in 2004, freezing degree-days per year
exceeded the thawing degree-days per year, and, by 2005, the thawing degree-days per
year had exceeded the freezing degree-days.
Statistical regression analysis, using 95% confidence interval, was performed for
the entire 1987 to 2007 (excluding 2003) degree-days. Regression analysis for the
thawing degree-days from 1989 to 2007 (excluding 2003) had a p-value of 0.101
suggesting the trend was not statistically significant, with standard deviation of 195.552
and R2
value of 0.173. Regression analysis using 95% confidence interval showed that
freezing degree-days from 1989 to 2007 (excluding 2003) had a p-value of 0.014
suggesting that the trend is statistically significant, with standard deviation of 248.453
and R2
value of 0.314. Overall, the number of thawing degree days did not change
68
significantly between 1987 and 2007 whereas there was a significant decrease in the
number of freezing degree days over the same period.
4.5 Stefan Depth and Permafrost Table Results (1989-2007)
The Stefan depth to the permafrost table and thermal offset were calculated using
the degree-days from Figures 11 & 12 with Equations 4, 5, 6 and 7 for the periods
between 1989 to 2002 and 2004 to 2007. The Stefan depth for freezing, Df, and thawing,
Du, layers were used to calculate the thermal offset in determining the permafrost state.
Various soil thermal conductivity (λ) values for various substrates dominating Arctic
soils were considered in calculating the results, such as sand (porous, non-porous), clay
and peat soils. The soil thermal conductivities of Du (λu) reflect dry theoretical summer
conditions of 0% soil moisture content, representing a lesser thermal offset effect (Figure
13; Nixon & McRoberts, 1973). The soil thermal conductivities of Df (λf) were adjusted
by 1.5 times the values of Du to represent the thermal offset effect of moist soils of 20%
soil moisture content (Figure 13; Nixon & McRoberts, 1973; Kujala et al., 2007).
69
Figure 13 - Thermal conductivity to water content for fine-grained soils, both frozen and
thawed soils (Nixon & McRoberts, 1973).
Since palsas have more organic matter and higher soil moisture content (30% soil
moisture content), the soil thermal conductivity was adjusted by 1.75 times the dry value
to represent an enhanced thermal offset effect (Figure 13; Nixon & McRoberts, 1973;
Kujala et al., 2007).
70
4.5.1 Porous Sandy Soils (1989 to 2007)
For Arctic soils dominated by porous sand (porosity >0.33) and given the degree-
day conditions from Figures 11 and 12 from 1989 to 2007, the thermal offset results were
calculated from the Stefan depths using Equations 4, 5, 6 and 7 (Figure 14 & Table 14).
Thermal Offset in Sand (Porosity >0.33) 1989 - 2007
-0.400
-0.300
-0.200
-0.100
0.000
0.100
0.200
0.300
0.400
0.500
1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008
Year
Th
erm
al
Off
set
Df
- D
u (
m)
Thermal Offset Df - Du (m)
Figure 14 – Thermal Offset for Sand (Porosity >0.33) Compositions 1989-2007
Table 14 – Results: Stefan Depths for Porous Sand (Porosity >0.33) Soil Compositions (1989-2002)
Stefan Depth - Permafrost Table (1989 - 2002)
Sand (Porosity >0.33) λ(F) = 1.99x1.5, λ(U) = 1.99
Year Df (m) Du (m)
Thermal Offset
Df - Du (m)
1989 1.579 1.157 0.422
1990 1.551 1.184 0.368
1991 1.486 1.231 0.255
1992 1.438 1.091 0.347
1993 1.419 1.198 0.221
1994 1.434 1.239 0.194
1995 1.354 1.147 0.207
1996 1.461 1.217 0.244
1997 1.328 1.243 0.085
1998 1.109 1.309 -0.200
1999 1.166 1.258 -0.092
71
2000 0.927 1.176 -0.249
2001 1.306 1.360 -0.054
2002 1.277 1.171 0.106
From 1989 to 1997, the depth of annual freezing of Arctic soils dominated by
porous sand generally exceeded the depth of annual thawing leading to a positive thermal
offset value (Table 14). This favoured permafrost conditions to freezing, interannual
accumulation, by a mean of 0.260 metres (STD = 0.103) over the 9-year span (Table 14).
After 1998, the depth of annual thawing exceeded the depth of annual freezing
leading to a negative thermal offset value, permafrost unfavorable conditions, by a
maximum of 0.249 metres of thawing in 2000 in arctic soils dominated by porous sand
(Table 14).
For Arctic soils dominated by porous sand from 2004 to 2007 and given the
degree-day conditions from Figure 12, the thermal offset results showed depth of annual
freezing of Arctic soils dominated by porous sand generally exceeded the depth of annual
thawing leading to a positive thermal offset value (Table 15).
Table 15 - Results: Stefan Depths for Porous Sand (Porosity >0.33) Soil Compositions (2004-2007)
Stefan Depth - Permafrost Table (2004 - 2007)
Sand (Porosity >0.33) λ(F) = 1.99x1.5, λ(U) = 1.99
Year Df (m) Du (m)
Thermal Offset
Df - Du (m)
2004 1.276 1.027 0.249
2005 1.490 1.343 0.148
2006 1.056 1.330 -0.274
2007 1.379 1.307 0.072
This favoured permafrost conditions for freezing by a mean of 0.49 metres (STD
= 0.227) over 4 years from 2004 (Table 15). In 2006 and onwards, the depth of annual
72
thawing exceeded the depth of annual freezing leading to a negative thermal offset value,
loss of permafrost, of 0.274 meters of thawing in porous sandy arctic soils (Table 15).
4.5.2 Non Porous Sandy Soils (1989 to 2007)
In Arctic soils dominated by non-porous sand (porosity <0.33) and given the
degree-day conditions from Figures 11 and 12 from 1989 to 2007, the thermal offset
results were calculated using Stefan depths and Equations 4, 5, 6 and 7 (Figure 15; Table
16).
Thermal Offset in Sand (Porosity <0.33) 1989 - 2007
-0.300
-0.200
-0.100
0.000
0.100
0.200
0.300
0.400
1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008
Year
Th
erm
al
Off
se
t D
f -
Du
(m
)
Thermal Offset Df - Du (m)
Figure 15 – Thermal Offset for Sand (Porosity <0.33) Compositions 1989-2007
73
Table 16 – Results: Stefan Depths for Non-Porous Sand (Porosity <0.33) Soil Compositions (1989-
2002)
Stefan Depth - Permafrost Table (1989 - 2002)
Sand (Porosity <0.33) λ(F) = 0.787x1.5, λ(U) = 0.787
Year Df (m) Du (m)
Thermal Offset
Df - Du (m)
1989 0.993 0.728 0.265
1990 0.976 0.744 0.231
1991 0.934 0.774 0.160
1992 0.905 0.686 0.218
1993 0.892 0.753 0.139
1994 0.902 0.779 0.122
1995 0.852 0.721 0.130
1996 0.919 0.765 0.153
1997 0.835 0.781 0.054
1998 0.697 0.823 -0.126
1999 0.733 0.791 -0.058
2000 0.583 0.740 -0.157
2001 0.821 0.856 -0.034
2002 0.803 0.737 0.067
From 1989 to 1997, the depth of annual freezing of non-porous sandy arctic soils
generally exceeded the depth of annual thawing leading to a positive thermal offset value
(Table 16). This favoured permafrost conditions to freezing, interannual accumulation, by
a mean of 0.164 metres (STD = 0.065) over the 9-year span (Table 16).
After 1998, the depth of annual thawing exceeded the depth of annual freezing
leading to a negative thermal offset value, permafrost unfavorable conditions, by a
maximum of 0.157 metres of thawing in 2000 in non-porous sandy soils (Table 16).
For arctic non-porous sandy soils and given the degree-day conditions from
Figure 12 from 2004 to 2007, the thermal offset results showed depth of annual freezing
generally exceeded the depth of annual thawing leading to a positive thermal offset value
(Table 17).
74
Table 17 – Results: Stefan Depths for Non-Porous Sand (Porosity >0.33) Soil Compositions (2004-
2007)
Stefan Depth - Permafrost Table (2004 - 2007)
Sand (Porosity <0.33) λ(F) = 0.787x1.5, λ(U) = 0.787
Year Df (m) Du (m)
Thermal Offset
Df - Du (m)
2004 0.802 0.646 0.157
2005 0.937 0.844 0.093
2006 0.664 0.836 -0.172
2007 0.867 0.822 0.045
This favoured permafrost condition to freezing by a mean of 0.031 metres (STD = 0.143)
over the four years (Table 17).
In 2006, the depth of annual thawing of Arctic soils dominated by non-porous
sand exceeded the depth of annual freezing led to a negative thermal offset value, loss of
permafrost, of 0.172 meters of thawing (Table 17).
4.5.3 Clay Soils (1989 to 2007)
For Arctic soils dominated by clay and given the degree day conditions from
Figure 11 from 1989 to 2002, the thermal offset results were calculated using Equations
4, 5, 6 and 7 (Figure 16; Table 18).
75
Thermal Offset in Clay 1989 - 2007
-0.200
-0.150
-0.100
-0.050
0.000
0.050
0.100
0.150
0.200
0.250
0.300
1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008
Year
Th
erm
al
Off
se
t D
f -
Du
(m
)
Thermal Offset Df - Du (m)
Figure 16 – Thermal offset for Clay Compositions 1989-2007
Table 18 – Results: Stephan Depths for Clay Soil Compositions (1989-2002)
Stefan Depth - Permafrost Table (1989 - 2002)
Clay λ(F) = 0.755x1.5, λ(U) = 0.755
Year Df (m) Du (m)
Thermal Offset
Df - Du (m)
1989 0.972 0.713 0.260
1990 0.956 0.729 0.226
1991 0.915 0.758 0.157
1992 0.886 0.672 0.214
1993 0.874 0.738 0.136
1994 0.883 0.763 0.120
1995 0.834 0.707 0.128
1996 0.900 0.750 0.150
1997 0.818 0.765 0.053
1998 0.683 0.806 -0.123
1999 0.718 0.775 -0.057
2000 0.571 0.725 -0.154
2001 0.805 0.838 -0.033
2002 0.787 0.721 0.065
76
From 1989 to 1997, the depth of annual freezing of clay soils generally exceeded
the depth of annual thawing leading to a positive thermal offset value (Table 18). This
favoured permafrost conditions to freezing, interannual accumulation, by a mean of 0.160
metres (STD = 0.063) over the 9-year span (Table 18).
After 1998, the depth of annual thawing exceeded the depth of annual freezing for
clay soils leading to a maximum negative thermal offset value, permafrost unfavorable
condition, of 0.154 metres of thawing in 2000 (Table 18).
For clayey soils and given the degree-day conditions from Figure 12 from 2004 to
2007, the thermal offset results showed depth of annual freezing of clay soils generally
exceeded the depth of annual thawing leading to a positive thermal offset value (Table
19).
Table 19 – Results: Stefan Depths for Clay Soil Compositions (2004-2007)
Stefan Depth - Permafrost Table (2004 - 2007)
Clay λ(F) = 0.755x1.5, λ(U) = 0.755
Year Df (m) Du (m)
Thermal Offset
Df - Du (m)
2004 0.786 0.633 0.153
2005 0.918 0.827 0.091
2006 0.651 0.819 -0.169
2007 0.849 0.805 0.044
This favoured permafrost condition to freezing by a mean of 0.030 metres (STD = 0.140)
since 2004 (Table 19).
In 2006, the depth of annual thawing for Arctic soils dominated by clay soils
exceeded the depth of annual freezing, leading to a negative thermal offset value, loss of
permafrost, of 0.169 meters of thawing (Table 19).
77
4.5.4 Peat and Organic Materials (1989 to 2007)
In Arctic soils dominated by peat with other organic matter and given the degree-
day conditions from Figure 11 from 1989 to 2002, the thermal offset results were
calculated using Equations 4, 5, 6 and 7 (Figure 17; Table 20).
Thermal Offset in Peat 1989 - 2007
-0.150
-0.100
-0.050
0.000
0.050
0.100
0.150
0.200
0.250
1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008
Year
Th
erm
al
Off
se
t D
f -
Du
(m
)
Thermal Offset Df - Du (m)
Figure 17 – Thermal Offset for Peat Compositions 1989-2007
From 1989 to 1997, the depth of annual freezing of peat generally exceeded the
depth of annual thawing leading to a positive thermal offset value (Table 20). This
favoured permafrost conditions to freezing, interannual accumulation, by a mean of 0.109
metres (STD = 0.043) over the 9-year span (Table 20).
78
Table 20 – Results: Stefan Depths for Peat Compositions (1989-2002)
Stefan Depth - Permafrost Table (1989 - 2002)
Peat λ(F) = 0.352x1.5, λ(U) = 0.352
Year Df (m) Du (m)
Thermal Offset
Df - Du (m)
1989 0.664 0.487 0.177
1990 0.652 0.498 0.155
1991 0.625 0.518 0.107
1992 0.605 0.459 0.146
1993 0.597 0.504 0.093
1994 0.603 0.521 0.082
1995 0.570 0.482 0.087
1996 0.614 0.512 0.103
1997 0.558 0.523 0.036
1998 0.466 0.551 -0.084
1999 0.491 0.529 -0.039
2000 0.390 0.495 -0.105
2001 0.549 0.572 -0.023
2002 0.537 0.493 0.045
After 1998, the depth of annual thawing exceeded the depth of annual freezing for
Arctic soils dominated by peat leading to a maximum negative thermal offset value,
permafrost unfavorable condition of 0.105 metres of thawing in 2000 (Table 20). In
Figure 12 from 2004 to 2007, the thermal offset results were calculated using Equations
4, 5, 6 and 7 (Table 21).
Table 21 – Results: Stefan Depths for Peat Compositions (2004-2007)
Stefan Depth - Permafrost Table (2004 - 2007)
Peat λ(F) = 0.352x1.5, λ(U) = 0.352
Year Df (m) Du (m)
Thermal Offset
Df - Du (m)
2004 0.537 0.432 0.105
2005 0.627 0.565 0.062
2006 0.444 0.559 -0.115
2007 0.580 0.550 0.030
79
The depth of annual freezing of Arctic soils dominated by peat generally
exceeded the depth of annual thawing leading to a positive thermal offset value by a
mean of 0.021 metres (STD = 0.095) since 2004 (Table 21). In 2006, the depth of annual
thawing for Arctic soils dominated by clay soils exceeded the depth of annual freezing
leading to a negative thermal offset value, loss of permafrost, of 0.115 meters of thawing
(Table 21).
In palsa areas dominated in peat material with high soil moisture content and
given the degree-day conditions from Figures 11 and 12 from 1989 to 2007, the thermal
offset results were calculated using Equations 5, 6, 7 and 8 (Figure 18; Table 22).
Thermal Offset in Palsas (Dense Peat) 1989 - 2007
-0.100
-0.050
0.000
0.050
0.100
0.150
0.200
0.250
0.300
1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008
Year
Th
erm
al
Off
se
t D
f -
Du
(m
)
Thermal Offset Df - Du (m)
Figure 18 – Thermal Offset for Palsa (Dense peat) Compositions 1989-2007
80
Table 22 – Results: Stefan Depths for a Palsa Formation (1989 – 2007)
Stefan Depth - Permafrost Table (1989 - 2007)
Peat λ(F) = 0.352x1.75, λ(U) = 0.352
Year Df (m) Du (m)
Thermal Offset
Df - Du (m)
1989 0.717 0.487 0.230
1990 0.705 0.498 0.207
1991 0.675 0.518 0.157
1992 0.653 0.459 0.194
1993 0.644 0.504 0.141
1994 0.651 0.521 0.130
1995 0.615 0.482 0.133
1996 0.664 0.512 0.152
1997 0.603 0.523 0.081
1998 0.504 0.551 -0.047
1999 0.530 0.529 0.001
2000 0.421 0.495 -0.074
2001 0.593 0.572 0.021
2002 0.580 0.493 0.088
2004 0.580 0.432 0.148
2005 0.677 0.565 0.112
2006 0.480 0.559 -0.080
2007 0.626 0.550 0.077
From 1989 to 2002, the depth of annual freezing of peat generally exceeded the
depth of annual thawing leading to a positive thermal offset value (Table 22). This
favoured permafrost conditions to freezing by a mean of 0.101 metres (STD = 0.094)
over the 14-year span (Table 22). In 1998 and 2000, the depth of annual thawing
exceeded the depth of annual freezing for Arctic soils dominated by peat leading to a
negative thermal offset value, permafrost loss of 0.047 and 0.074 metres, respectively,
from thawing (Table 22).
81
4.6 Soil Moisture Content Loss Test (2008)
The results from a soil moisture control loss test using nine (9) control soil
containment samples were accomplished to simulate the loss of soil moisture over a five
(5) week period was conducted for the 2008 sampling campaign from March to April
2009.
The results showed an mean loss of 4.4 millilitres of moisture from samples in
double and triple containment (Table 23). All samples showed decreasing results in water
volume, the least being from T5 with a loss of -2.8 millilitres and the most with T6 at -6.9
millilitres over 5 weeks (Table 23).
Table 23 – Results: Soil Moisture Content Loss Test (2008)
Control
ID
Initial Water
Mass Mbw
(Total) (g)
After-5
Weeks
Water mass
M5wks (g)
Change in
Water
Mass (g)
Water
Density at
23C (g/mL)
Volume
Loss
(mL)
T1 54.2 50.9 -3.3 0.9976 -3.3
T2 54.2 50.8 -3.4 0.9976 -3.4
T3 54.0 48.5 -5.5 0.9976 -5.5
T4 54.1 50.4 -3.7 0.9976 -3.7
T5 63.8 61.0 -2.8 0.9976 -2.8
T6 53.5 46.6 -6.9 0.9976 -6.9
T7 54.1 48.0 -6.1 0.9976 -6.1
T8 53.9 49.9 -4.0 0.9976 -4.0
T9 63.8 60.0 -3.8 0.9976 -3.8
MEAN 56.2 51.8 -4.4 --- -4.4
STD 4.3 5.1 1.4 --- 1.4
82
CHAPTER 5: Discussion
5.1 Soil Characterization
The soil samples retrieved from the study sites were visually analyzed and
described based on visible characteristics of the soil, the composition, presence of soil
organic matter, and with analyses on acidity and the gravimetric soil moisture content.
Acidity and soil moisture content (SMC) measurements from 2007 and 2008 have
revealed acidic to neutral conditions (pH ~ 4 to 7) and variation in soil moisture content
(SMC ranged between 20 to 60%). Characterization of the accompanying soil sampling
sites revealed the presence of soil organic matter, living and decomposing plant residues,
and various moss and lichen compositions. Inland samples had low acidic pH values, the
presence of soil organic matter, and the soil was dominantly clayey. Soil samples near the
shores of Hudson Bay contained sandy soil and were slightly basic having a higher pH
value.
The majority of the analyzed samples collected from the inland sampling sites in
Northern Ontario from 2007 and 2008 contained high contents of organic matter (Tables
4 and 5). Sphagnum and partially decomposed plant material was the major composition
of the samples. Plant materials discovered included decomposing stems, roots, and
leaves. Inorganic materials found in the samples were rocks and mineral sediments
(Tables 4 and 5). Samples found with high organic matter content, based on the site
descriptions, had a lower pH value (pH of 4.41 from the 2007 campaign and pH of 6.17
from the 2008 campaign); suggesting acidic conditions (Tables 6, 7 and 8). Decomposing
organic materials can release organic acids in moist conditions (Zoltai & Witt, 1995).
Gravimetric soil moisture content was higher for samples and sites with abundant organic
83
material located in clayey and silty soils. High gravimetric soil moisture content
(SMC~60%) conformed to high moisture conditions observed in the wet Hudson Bay
lowland area, as there were abundant vegetation and organic material that can lead to a
greater affinity for water in soils (Tables 6 and 8). The presence of peat formations,
Sphagnum, grasses and ideal soil compositions provide favourable conditions for the
inland soils to retain soil moisture content. A relatively high soil moisture conditions for
an inland site was observed at B5 with a gravimetric soil moisture content of 94% and
pH~6 being ~50 km inland from the nearest Hudson Bay shore (Tables 5 and 7). Site B5
was highly organic which can withhold water molecules in the soil pore space (Seppälä,
2003). Based on the field notes provided from Gough, most of the samples with acidic
conditions were extracted from sites situated in fens and bogs (Tables 4 and 5). Zoltai &
Witt (1995) suggested that fens and bogs have relatively low pH due to high degradation
rates of organic matter contents in which supports the findings of the site soil
characterizations.
The majority of the analyzed soil samples collected along the Hudson Bay coastal
sites in Northern Ontario were dominated by sandy and gravelly soils (Tables 4 and 5).
There were little traces of soil organic matter. The observed organic material was
observed from samples retrieved near the soil surface composed of primarily partially
decomposed plant matter. The plant materials discovered included decomposing stems,
roots, and peat. The dominant inorganic materials found in the samples were rocks and
sediments ranging from sizes of pebbles (~ 10 mm in diameters) to gravel (~30 mm). The
observed rocks were rounded and smoothed due to the processes of weathering and
erosion from the shore and atmospheric actions. This area also experiences seasonal
84
freezing and thawing cycles. The sediments were unsorted resulting in conglomerate of
different sizes, shapes and colours. The low gravimetric soil moisture content (~20%) for
the coastal samples, in comparison to the inland gravimetric soil moisture content, can be
attributed to the poor water retaining ability of sand and gravel with the lack of abundant
organic material and clay minerals (Eyles & Miall, 2007; Tables 6 and 7). Without
decomposing soil organic matter to produce humic acids, the coastal samples resulted in a
higher mean pH value of 7.14 then compared to the inland pH of 6.17; basic conditions
(Tables 6 and 8). Weathering and chemical erosion of rocks, parent material and glacial
sediments can produce a moderate base (Eyles & Miall, 2007).
Highly organic soils with high soil moisture contents can undergo considerable
frost heaving by the formation of ice lenses that expand the soil volume (Guglielmin et
al., 2008; Kuhry, 2008). The observation of palsas in the Hudson Bay Lowlands provides
direct evidence to support frost heaving and the formation of ice lenses. However the
presence of excess soil moisture content for palsa development suggests warmer
conditions in the area followed by sufficient seasonal cooling to provide freezing, this
imply significant changes per season in the thickness of soils due to heaving and melting
that can modify the topography (Thie, 1974; Gross et al., 1990; French, 1999; Henry,
2000; Spielvogel et al., 2004; Kim et al., 2008; Larsen et al., 2008; Wang et al., 2009).
85
5.2 Freezing and Thawing Degree-Days
The freezing and thawing degree-days were determined using actual weather data
from Peawanuck weather station in Northern Ontario. The threshold in determining
freezing and thawing was set at 0ºC. As shown in Figure 11, in the span of 14 years from
1989 to 2002 the number of freezing degree-days had decreased with statistical
significance (r = -0.812, R2 = 0.660; p-value = 0.000; Table 12). The lowest number of
freezing degree-days was calculated at 557 for the year of 2000 (Figure 11). For the
thawing degree-days with minor variation was observed over the 14-year span (p-value =
0.106; STD = 163.93; Table 12). The thawing degree-days increased to a peak number of
days of 1,798 calculated for the year of 2001 before decreasing near the mean thawing
degree-days for 2002 (Figure 11 & Table 12).
The freezing and thawing degree-days was calculated for a second interval of 4
years from 2004 to 2007, this was due to the incomplete temperature data provided by the
Peawanuck weather station during 2003 (Figure 12); this is further discussed in Section
5.8 Sources of Error & Uncertainties. As shown in Figure 12, in the span of 4 years from
2004 to 2007 the number of freezing degree-days had slightly increased, however this
was not statistically significant (r = 0.077, R2 = 0.006; p-value = 0.920; Table 13). The
lowest number of freezing degree-days was calculated at 722 for the year of 2006 (Figure
12). A sharp increasing trend was observed for the thawing degree-days from the years
2004 to 2005 with minor variation afterwards, however this was not statistically
significant (p-value = 0.105; Figure 12). The thawing degree-days had increased to a
peak number of days of 1,751 calculated for the year of 2005 before slightly decreasing
to 1,659 thawing degrees days for year of 2002 (Figure 12 & Table 12).
86
An analysis of the degree-day trends for Peawanuck, Northern Ontario has shown
that since 1993, the numbers of thawing degree-days have exceeded the numbers of
freezing degree-days, suggesting a warming trend in the region (Figure 11). With
increased number of thawing degree-days and decreased number of freezing degree-days
(T-test two-tailed p-value = 0.002; Figures 11 and 12), climatic and environmental
conditions have become unfavourable for permafrost presence. As this region is located
in the southern portion of the Arctic and parts in the Subarctic, the permafrost state in the
region is likely and most susceptible to be in decline. This degradation of permafrost
would be amplified in surface areas without vegetation and organic layers that could
provide insulation against thawing energies.
5.3 Stefan Depth and Permafrost Table
The Stefan depth of freezing (Df) and thawing (Du) were used to calculate the
thermal offset (Df - Du) to provide an estimate of the thickness of the active layer and
permafrost with projections of the permafrost table (Tables 14 to 21). In the winter
season, dominated by negative ground heat flux, the freezing energies can penetrate down
the soil column represented by the Stefan depth of freezing derived from freezing degree-
day with temperatures less than 0°C. This provided a seasonal estimate of the depth of
soil susceptible to freezing. In the spring-summer seasons, thawing of the active layer
begins when sufficient incoming solar radiation and geothermal heats allows for a
positive ground heat flux state (Ling & Zhang, 2004; Carey et al., 2007; Hayashi et al.,
2007). The geothermal heating at the permafrost base is not discussed in this thesis.
Heating from the atmosphere will first remove the insulating snow cover from the surface
87
before thawing the active layer (Muller, 2008; Zhang et al., 2008b). The depth of thawing
is determined with the Stefan depth of thawing calculation.
In areas south of the subarctic, it is typical to have a negative thermal offset (Du >
Df) condition (Burns & Smith, 1987; Duan & Naterer, 2009). This represents seasonal
freezing during the winter season followed by a complete thawing of the soils in the
summer season. When the seasonal Stefan depth of thawing does not exceed the seasonal
Stefan depth of freezing (Du < Df), the resulting positive thermal offset represents the
theoretical thickness of a frozen layer of soil that has persisted over the summer thawing
season, and has survived into the next freezing cycle (Burns & Smith, 1987; Duan &
Naterer, 2009). Since permafrost is defined as permanently frozen soils that remain
frozen for at least two consecutive years, this layer of frozen soil must persist through a
second summer-thawing cycle (Gough & Leung, 2002; Shur & Jorgenson, 2007; Muller,
2008). If the positive thermal offset (Du < Df) condition persists over two warming
seasons, the soil state would be classified as the development of permafrost or permafrost
present (Burns & Smith, 1987; Duan & Naterer, 2009). In regions with continuous
permafrost zones, such as in the Arctic, positive thermal offset conditions will lead to the
thickening of the permafrost layer (Burns & Smith, 1987; Duan & Naterer, 2009).
Negative thermal offset conditions in the Arctic will lead thinning of the permafrost layer
and the development of thicker summer active layers; the permafrost table represents the
interface at which the extent of the depth of thawing ends and meets the permafrost layer
(Burns & Smith, 1987; Muller, 2008; Duan & Naterer, 2009). In discontinuous
permafrost zones such as in the Subarctic, negative thermal offset conditions can result in
the disappearance of permafrost.
88
The Stefan depths calculation, using Equation 4 required the soil thermal
conductivity (λ). Soil thermal conductivity is strongly influenced by the soil moisture
content and the type of soils. Calculations of Stefan depths were categorized based on the
typical composition of Cryosols that dominated by sand (porous and non porous), clay,
and an organic top layer, peat. Theoretical dry soil conductivities (0% soil moisture
content) were assigned to the four categories as follows: porous sand (λ = 1.99), non-
porous sand (λ = 0.787), clay (λ = 0.755) and peat (λ = 0.352). The thermal conductivities
for moist (20% soil moisture content) and frozen soils were increased by a factor of 1.5 to
the dry soil conductivities (Nixon & McRoberts, 1973; Kujala et al., 2007). The dry soil
thermal conductivities, representing warm summer soil conditions, were applied in the
Stefan Equation to calculate depth of thawing (Du) (Equation 5). The enhanced thermal
conductivities for moist and frozen soils represented the winter conditions in calculating
the Stefan depth of freezing (Df) equation (Equation 6). The generalized soil
conductivities were applied, as there were no accessible previous soil investigations
conducted in study area. Peat was identified as a thermal insulator resulting as having the
least conductivity. The greatest conductivity was assigned to porous sand due to the large
porosity (typically 33%) and high soil water capacity (Dunne & Leopold, 1978; Price &
Waddington, 2000).
The study area is located in the continuous permafrost zone (along the shores of
Hudson Bay) and in the region of discontinuous permafrost (further inland in Northern
Ontario). The thermal offset values can be applied as an annual change to permafrost
thickness (Burns & Smith, 1987; Natural Resources Canada, 2006). In general, the
results of the thermal offsets showed positive thermal offset conditions favourable to
89
permafrost in the years from 1989 to 1997, 2002 to 2005 and 2007; the remaining years
(excluding 2003) showed negative thermal offset values (Tables 14 to 22). The greatest
thermal offset was experienced in the porous sandy soils due to the high soil conductivity
value (Tables 14 and 15). The least thermal offset was experienced by organic peat layer
due to the low soil conductivity value and thermal insulating properties (Tables 20 and
21).
5.4 Permafrost Presence
Using the Stefan depth calculations for permafrost (Equation 4) and the degree-
days, extracted from weather station data, from 1989 to 2007 (Figures 11 and 12), the
thermal offset was calculated to determine the change in permafrost thickness. Actual
depths to permafrost were measured during the 2007 and 2008 field sampling campaigns
(Figure 5). Mechanically in 2007 field campaign, permafrost was deemed present when a
graded metal rod could no longer be drilled into the subsurface (Figure 6). Difficulties
can arise in differentiating the impact of the rod on the permafrost table or with a buried
obstruction, such as a rock or an ice lens (Mühll et al., 2002). The presence of permafrost
in 2008 was determined using thermistor probes that were lowered into an augured
borehole (Figure 7). The thermistor measured ground soil temperature and recorded the
temperature range on a data logger. When the soil temperature was reported near or at
0°C, the sample site was deemed to be permafrost present (Smith & Burgess, 2002;
Nicolsky et al., 2009).
Annual depth to permafrost measurements provides monitoring information of the
active layer thickness and the state of the permafrost at the study sites (Nicolsky et al.,
90
2009). Using this information, trends can be used to assessment the future state of
permafrost for the region such as estimating the mean reduction of permafrost and the
extension of the active layer (Anisimov & Nelson, 1996; Nicolsky et al., 2009; Pang et
al., 2009). Averaged depths to permafrost were calculated from the measured sampling
points located in each of the three quadrants in Table 11 to represent the western, central
and eastern portion of Northern Ontario and the shores of Hudson Bay (Tables 10-12). A
significant annual variation between the mean depth to permafrost of August 2007 and
2008 was observed (Figure 5; Table 11). In 2007, the depth to permafrost ranged between
40 to 50 centimetres while in 2008 the depth to permafrost ranged between 110 to 140
centimetres from the surface (Table 11; Figures 11 and 12). The results of 2008 were
roughly three times greater than the depths measured in 2007 which could be explained
due to different sampling strategies as there was a focus in the coastal regions for 2008
and inland for 2007; the coastal sites were dominated by sandy soils and the inland sites
contained greater organic material content. As observed in the 2008 results of the three
quadrants in Table 11 and Figure 7, there was a decrease in the depths to permafrost from
west to east, Quadrants 1 to 3, suggesting asymmetrical thawing of the active layer and
permafrost. The depth to permafrost measurements suggests thicker active layer
developments were experienced in Quadrant 1, an enhanced thawing event. In Quadrant
3, the influence of the peat and organic material may have insulated and reduced the
thawing energies on the active layer and permafrost. In comparison to the 2007 mean
depth to permafrost results in Table 11, Quadrant 3 experienced less thawing than
compared to Quadrant 2. A direct explanation of these trends for Quadrant 3 was not
investigated for this thesis and further research in area should be conducted.
91
Based on the descriptions listed in Table 4 and 5, highly vegetated areas and high
organic matter in the soil composition was documented as distance progressed inland
with the sample sites. The highly organic layer of peat and vegetation above the active
layer could provide thermal insulating benefits (Thie, 1974; Hinkel et al., 2001; Cheng et
al., 2004; Spielvogel et al., 2004; Martini, 2006; Zhang et al., 2008b; Pang et al., 2009).
Based on the results in Table 8, the high organic composition observed at the sample sites
could provide thermal insulation for permafrost against heat energy penetrations through
the active layer and reduced the severity of thawing in the summer. In the winter, an
upper snow layer above the soil provides an additional thermal insulation that can prevent
freezing energies, increase thermal resistance, from entering the soil column to enhance
the permafrost (Cline, 1997; Cheng et al., 2004; Osterkamp, 2005; Zhang et al., 2008b).
Lowland areas in bogs and fens have significant organic matter and soil moisture that
allowed well-aggregated conditions to further retention of soil water in the soil pores
(Juma, 2006; Carey et al., 2007; Kim et al., 2008; Kuhry, 2008). However, as
established with Shur & Jorgenson (2007), an increase in soil moisture content could
result in an increase in thermal conductance of energy with respect to different soil
compositions.
Near the shores of Hudson Bay, active layer thawing depth were seen to be higher
than inland, this can be attributed to the low organic matter content, sandy soil
composition with moderate moisture conditions near the body of water (Table 7 and
Figure 5). Without the high organic matter composition, a thermal insulating layer cannot
be effectively established over the active layer. Sandy and moist soils enhance the soil
92
conductivity and allow further penetration of heat energy into the soil column resulting in
a greater Stefan depth of thawing (Tables 14 to 17).
Acidity in the inland soils ranges from pH of 5 to 7 and remains acidic conditions
of the soil samples in Tables 6 & 8 could be attributed to the organic matter content in
Tables 4 & 5 possibly due to the production of organic and humic acids. Since the study
area is located on the Canadian Shield as the parent bedrock material, there is little
capacity for chemical dissolution to provide buffer conditions for the soils (Eyles &
Miall, 2007).
Thermal offset calculations from the degree-days observed at Peawanuck revealed
permafrost to be in a fluctuating state of freezing and degradation with high degradation
rates to have occurred from 1998 to 2001 before recovering to a positive thermal offset.
In the summer months, permafrost unfavourable conditions exist as air temperatures are
above freezing allowing the growth of the active layer (Shur & Jorgenson, 2007). Over
winter, permafrost growth by incorporation of the active layer base can occur when
conditions favour permafrost development (Shur & Jorgenson, 2007). Overall, there was
a negative thermal offset in 2006, resulting in a reduction of permafrost thickness by a
minimum of 0.115 metres in peaty soil and a maximum of 0.274 metres in sandy soils
(Tables 16 and 21). With further studies on thermal offset in this region, prediction of the
permafrost fate along the shores of Hudson Bay and in the Northern Ontario region can
be projected.
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5.5 Palsa Presence
Shallow active layers above the permafrost were observed in palsas with highly
acidic and moist characteristics due to the organic matter content (Figure 19). In moist
conditions, thermal conductance can be enhanced for heat transfers to the soil column.
For the palsas observed in July and August of 2007 and 2008, the organic top layer of
Sphagnum species and peat formations served as an insulating layer that prevented
further energy penetration from the atmosphere to the soil. Based on the field notes,
palsas were situated in fens, bogs and peat lands that are high in moisture and organic
matter (Tables 4 and 5). Soil samples collected from palsas contained higher soil
moisture contents. The thick organic layers did protect against permafrost degradation by
reducing the severity of heat energy penetration (Figure 19; Tables 6 & 21). The layer of
organic material can enhance freezing of soil moisture in the winter causing the
expansion and raised soil column to form the circular mounds (Kujala et al., 2007;
Kuhry, 2008). Palsa acidity ranges more broadly from a pH of near 3 to a pH of 7 (Tables
4 and 6). The analysis of the freezing and thawing degree-days showed a change in the
1990s where the number of thawing degree-days has exceeded the freezing degree-days
suggesting unfavourable climatic conditions for permafrost and palsas. However, even in
the summer, palsas are able to remain intact and present in the landscape possibly due to
the enhanced organic peat layer protection.
Due to limitation on literature surrounding the interactions of palsas in nature, the
exact purposes of these features remain understudied and not well understood. Palsas
may have an ecological role in the habitat of Polar bears. Field notes from both 2007 and
2008 have reported disturbed palsa, possibly due to polar bear activity in the region in
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search of den locations or for cooling purposes near the permafrost (Figures 19 & 21).
Female polar bears are known to exhibit site-fidelity behaviour for dens in Northern
Ontario (Crompton et al., 2008). With climate change and shifts in the terrain with
melting permafrost, the impact on inland polar bear food sources may lead to changes in
feed behaviour (Dyck et al., 2007; Callaghan, 2008). Dyck et al (2007) cautions that
impacts on polar bears from climate change is still not well understood as there are many
interconnected factors that can affect distribution, feeding behaviour, body mass and
survival; however, it should be noted that early breakup of sea ice experienced in Hudson
Bay may be a major factor in polar bear survival (Gagnon & Gough, 2005; Stirling et al.,
2008).
5.6 Addressing Research Question 1
• 1. Can the distribution of permafrost in Northern Ontario be rationalized using the
relationship between soil moisture content and the frozen and unfrozen soil
thermal conductivities, “the thermal offset” as hypothesized by Gough and Leung
(2002)?
By establishing relationships of soil thermal conductivity with soil moisture
content and thermal offset trends over time, using the Equation 7 from Burns & Smith
(1987), the presence of permafrost can be predicted. The presence of permafrost will
ultimately depend on the climate conditions that are favourable for permafrost formation
(Shur & Jorgenson, 2007). Continuous and discontinuous permafrost zonation can be
determined using the Frost number calculation from Equation 1 as suggested by Nelson
& Outcalt (1987); however, as shown in Gough & Leung (2002), there were
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discrepancies between calculated Frost Numbers with field observations in the Hudson
Bay Lowlands. The application of the thermal offset approach includes the soil moisture
effect that has shown support to the field observations (Tables 14 to 21; Gough & Leung,
2002). This research furthers the understanding of the presence of continuous permafrost
in Canada‟s subarctic region of Northern Ontario due to the thermal offset phenomenon
while calculations of Frost numbers and observations in southeastern Hudson Bay show
discontinuous permafrost. By using degree-days in this research in establishing the Stefan
depths of thawing and freezing, this allows the thermal offset to be calculated. Unlike the
Frost number, which aids in permafrost zone classification, the thermal offset allows
estimations on the direct changes to permafrost thickness. With available permafrost
thickness measurements and the thermal offset, a timeframe could be estimated using
projected climate scenarios to predict the fate of permafrost for a region. Since freeze-
thaw degree-days requires temperature data collected at weather stations, issues
pertaining to data quality arise from the use of transposed data from neighboring
locations to remote sites that lack a permanent weather station. This remains an academic
issue, as these temporal and spatial variations in temperature can lead to
misrepresentations in theoretical calculations that may not be represented with real world
observations, as seen in the application of the Frost number by Gough & Leung (2002).
Based on this research and the data provided, the thermal offset was calculated for
the Peawanuck region using various values of soil thermal conductivities based on
dominant arctic soil compositions. Temperature data was provided from a pre-existing
weather station at Peawanuck, Ontario, for this undertaking. Temperature data allowed
the calculations of the degree-days required for the Stefan depths equation that ultimately
96
allows for assessing the presence of permafrost through the thermal offset approach. To
determine the fate of permafrost and its future presence in this subarctic region both
climatological and environmental factors must be considered in order to represent the
complexities of natural system. Long-term monitoring of permafrost is necessary since
the behaviour of permafrost is seasonally and temporally dynamic, permafrost can
thicken over one winter, so that variation can lead to new depths to permafrost in the
following summer or completely melt. Important environmental factors that should be
considered are thermal insulation by organic matter and vegetation that can enhance and
protect permafrost thickness, prolonging permafrost presence. Biological activity is an
important factor that is difficult to assess, such as polar bears disturbances of the upper
and active layers that can have impacts on permafrost insulation (Figure 19). Inorganic
factors will have strong influences on the energy conductance of the soils above the
permafrost, such as soil composition, moisture content, and acidity. The resulting
complexity of the question proposed for this research has shown that with simplification
of nature, estimations and trends of permafrost presence and extent can be determined for
a region. The trend of the calculated thermal offset for Peawanuck, Ontario, suggested a
weak negative trend from the shores of Hudson Bay and inland into Northern Ontario;
this suggests greater permafrost shifts are likely to occur near the shores of Hudson Bay
where soils are dominant porous with sands and gravel, and where vegetation and organic
insulation and protection is weaker; less soil moisture also weakens the thermal offset
effect. Further inland in peaty and clayey soils, the thermal offset of permafrost showed a
weak negative trend suggesting events favourable to thawing however, the severity is
reduced due to the protective insulation layers of organic material and peat. For accurate
97
results, long-term monitoring, installation of weather stations in remote areas, and
geophysical methods in surveying permafrost should be adapted to provide better
resolution and include variables from all the physical factors influencing the permafrost.
5.7 Addressing Research Question 2
• Does the presence of palsas affect the thermal conductivity of soil from the
surface cover down to the permafrost?
The presence of palsas can affect the thermal conductivity of soil, from the
surface cover down to the permafrost, due to the high organic matter presence that has
affinity for soil moisture and provides a thermal insulation effect. The formation of palsas
resulted from the enhancement of the permafrost core from favourable conditions, such
as the insulating properties of vegetation and organic matter layers. Peat and mosses
prevent thermal conductance of heat energy in the summer air to the permafrost and
prevents permafrost degradation. The same process can enhance the cold penetration into
the palsa, via thermal offset, in the fall and winter seasons. If there is no insulating snow
cover, the enhanced cold penetration can freeze additional soil moisture and strengthen
the palsa formation. Based on the reviewed studies and the site characteristics conducted
from soil samples of palsas, there is evidence that suggests that the characteristics of the
thick organic layers above the active layer in a palsa does decrease thermal conductivity
of heat energy from the surface to the permafrost. In comparison of thermal offset results
for 2006 in Table 20, peat soil (-0.115 m), and Table 22, palsa formation (-0.080 m), the
additional organic material and soil moisture enhances the soil thermal conductivity by a
factor 1.75 (thermal offset effect) for the Stefan freezing depth allowing for a greater cold
98
penetration (0.480 m for palsa in comparison to 0.444 for peat soils) that reduces the
impact of the summer thawing penetration. Since only a few authors dominate the
scientific literature on palsas in general, further studies are crucial and necessary to
determine the role and thermal dynamics of palsas in the arctic. It should be noted that
from the field study, palsas may have a significant ecological role for polar bears as
evidence have suggested that polar bears have be attempting to construct habitats and
dens near and on palsas (Figure 19).
5.8 Sources of Error and Uncertainties
Traditional permafrost delineation methods involved drilling boreholes. Since
subsurface materials, such as the organic layer and unconsolidated sediment layers, are
not homogenous in nature, it is difficult to auger boreholes in moist soil conditions as the
integrity of the borehole walls may collapse. Utilizing an auger can generate heat in the
borehole along the walls and this may thermally contaminate the thermistor readings
leading to inaccurate soil temperature results. With this important error, soil temperatures
close 0ºC, up to 4ºC, were accepted as permafrost present.
The data collected from boreholes in the study area provided point-scale
resolution specific to the sampling site. The combination of multi-borehole data in this
analysis for the quadrants extrapolated the results between boreholes to produce data on a
regional scale. Since permafrost presence is site specific, up scaling to a larger scale
reduces the resolution of site-specific characteristics, and this up scaling technique
assumes a homogenous subsurface approach.
99
Sources of error for laboratory analytical methodology could be due to a time
difference between soil collection and laboratory analysis work in which there was a
month disjunction from August to October. A soil moisture control loss test of 9 control
samples was accomplished to simulate the loss of soil moisture through the sampling
containments over a one month period was conducted for the 2008 sampling campaign.
The results showed a mean loss of 4 millilitres of moisture from samples in single, double
and triple containment (Table 23). To rectify this error, an addition of a correction factor
of 7% was added to the measured gravimetric soil moisture values, also in millilitres, and
then converted to gravimetric soil moisture content in unit percentage.
Observation of the soil characteristics was extremely difficult to visually identify
as soil or peat due to partial decomposition; vegetation and fungus species proved
difficult to identify due to partial fragments and decomposition.
The gravimetric soil moisture content was conducted since this accepted method
allows for simple and direct measurements without bulk density information. Few soil
sample containments did leak and this may have altered the gravimetric soil moisture
content. Since the soil samples were not filled to the volume of the sample containers and
with the time difference, the bulk density of the soil could not be determined to convert
gravimetric soil moisture content to the volumetric soil moisture content.
In calculating the degree-days of freezing and thawing, temperature data from
1986 to 2007 was acquired from weather stations in the study area (Figure 2). Incomplete
yearly temperature data sets were examined and years with extreme gaps in data, greater
than 30 missing days, were omitted from the calculation. Temperature data sets from
1986 to mid-1988 and 2003 were incomplete and omitted (Figures 11 and 12). To ensure
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full data sets, missing days up to five consecutive days were corrected using linear
regression from the beginning and the end of the month. Individual missing days were
corrected using an arithmetic mean value of the temperature on the day before and after.
While determining the Stefan depths and thermal offset, the quality of degree-day
data was limited to the quality of the extracted temperature data. Uncertainty in the
temperature data could influence the final results of the thermal offset calculations. The
thermal offset calculation required values for soil conductivity, which could not be
determined at the time of soil sampling. Generalized soil thermal conductivities were
applied based on the literature review for Arctic soils and peat. With additional field data
on the soil composition and site characteristics, an accurate soil thermal conductivity
could be achieved by applying the de Vries Equation (Equation 2) that could be utilized
in the thermal offset estimations.
Using Geographical Information Systems (GIS), errors of significant digits may
have led to some inaccuracies in determining distances between the sample sites and the
Hudson Bay shore based on the map produced (Figures 5, 6 and 7). Electronic maps of
the Northern Ontario region used for this study were was geo-referenced from 1984 and
compiled in 1992. The study area and sampling region spanned over two Universal
Transverse Mercator coordinate systems, the UTM 16 and 17. UTM 16 was selected as
the projection in generating the map figures. Slight geographical shifts to the actual
sampling locations may have occurred with this selected projection.
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5.9 Potential Research Impacts on Society
The results from this undertaking established data for permafrost presence to be
estimate based on soil moisture content, temperature data and soil thermal conductivity
properties. Incorporating the results of this research in establishing physical relationships
of soil thermal conductivity in the development and degradation of permafrost can allow
models and predictions in the fate of permafrost. The region of Northern Ontario along
Hudson Bay is situated at the southern edge of the sub-Arctic zone. With climate
warming, this region is at the frontline of environmental change as shift in physical
properties of the permafrost can result in destabilizing structures erected on the
permafrost and palsa formation and degradation which is a significant safety risk for
northern communities of Canada (Vyalov et al., 1993; Sorochan & Tolmachev, 2006).
An ongoing concern in Arctic regions and northern communities pertains to
delineating and predicting the movement of contaminants in contaminated sites located in
continuous and discontinuous permafrost states (Delaney et al., 2001; Tsuji et al., 2001;
Kalinovich et al., 2008). With changes to the underlying permafrost, sites such as the
relic radar station at Winisk still possess potential subsurface contamination concerns
(Tsuji et al., 2001). The transitional layers between the active layer and permafrost table
forms finger-like grooves and channels (Eyles & Miall, 2007; Kalinovich et al., 2008).
With thawing of the active layer, the permafrost table becomes asymmetric (Delaney et
al., 2001; Kalinovich et al., 2008). Since permafrost is considered impermeable, these
finger-like grooves and asymmetric topography will influence the flow paths for
contaminants resulting in difficulties in delineating contaminated sites, especially, since
the permafrost table can have considerable temporal and spatial variability within one
102
freezing and thawing cycle of a year (Delaney et al., 2001; Tsuji et al., 2001; Eyles &
Miall, 2007; Kalinovich et al., 2008).
As Canada continues to develop northwards with the sub-Arctic being the
forefront of climate change, permafrost research can provide predictions and assessments
in determining the impacts of shifting ground. The processes of frost heaving and the
degradation of permafrost are continuing concerns to existing and future building
foundations and transportation infrastructures, which can be destabilized and cause risks
to human health and safety (Sorochan & Tolmachev, 2006; Eyles & Miall, 2007; Pang et
al., 2009). In the physical process of freezing soil water into ice, volumetric expansion
occurs in the soil with an increase in mechanical strength that can be compromised by
melting, and further exacerbated by resulting melt water (Eyles, 2006; Duan & Kim et
al., 2008; Duan & Naterer, 2009; Pang et al., 2009). Impacts can lead to ground
subsidence, settlement and infrastructure foundation failures that can cost significant
amount of damages and expenses for constructions, repairs, renovations and planning
(Ling & Zhang, 2004; Eyles, 2006; Sorochan & Tolmachev, 2006; Duan & Kim et al.,
2008; Jin et al., 2008; Larsen et al., 2008; Naterer, 2009). Permafrost predictions and
models have economical importance for civil construction and engineering of oil and gas
pipelines, for military infrastructure developments in Canada‟s Arctic regions, and for
transportation networks. Continuing permafrost research can further develop adaptation
methods by planners and engineers to improve the quality of life, reduce risks, and
improve safety for Canada‟s First Nation peoples and northern communities.
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CHAPTER 6: Conclusion
6.1 Permafrost
The dominant physical processes governing permafrost presence were identified
as: climate and environmental conditions, ground heat flux, and soil thermal conductivity
properties (Nixon & McRoberts, 1973; Burns & Smith, 1987; Halliwell & Rouse, 1987;
Nelson & Outcalt, 1987; Hinkel et al., 2001; Gough & Leung, 2002; Mühll et al., 2002;
Smith & Burgess, 2002; Cheng et al., 2004; Yoshikawa et al., 2004; Overduin et al.,
2006; Carey et al., 2007; Hayashi et al., 2007; Shur & Jorgenson, 2007; Kujala et al.,
2007; Kneisel et al., 2008; Muller, 2008; Zhang et al., 2008a; Duan & Naterer, 2009;
Nicolsky et al., 2009; Wang et al., 2009). Changes in these processes can either favour
permafrost formation, aggradation, or degradation. This supports the hypothesis
presented by Gough & Leung (2002), the analyses of the soil samples provided and the
literature reviewed suggest evidence that soil thermal conductivity has shown to play a
substantial role in permafrost presence in the Hudson Bay region. Both evidence from the
laboratory analyses and site descriptions in support of Shur & Jorgenson (2007) suggests
that soil moisture content can influence and enhance the conduction of energy through
the soil column. Since soil thermal conductivity is not a factor in the Frost number and
the rate of permafrost thawing equations, the use of Stefan Equation in determining the
thermal offset is appropriate for determining the state of permafrost (Burns & Smith,
1987). The Stefan depths utilize the number of freezing and thawing degree-days and
include the soil thermal conductivity that can be influenced by soil moisture content and
by soil compositions (Nixon & McRoberts, 1973; Nelson, 1986; Hayashi et al., 2007;
Hughes & Braithwaite, 2008). The complex interactions of soil organic matter enhances
104
soil moisture and acidic conditions, and that the layers of organic matter can provide
unique insulating effects that can protect and favour permafrost presence (Zoltai & Witt,
1995; Yoshikawa et al., 2004; Carey et al., 2007). Since 1993, there has been a shift in
Northern Ontario favouring a decreasing trend in freezing degree-days (p-value = 0.000;
Table 12).
This research concludes that permafrost is present in the Northern Ontario areas
dominated by organic materials such as peat with clayey soils. The organic material and
clayey soils provides high soil moisture content that enhances the soil thermal
conductivities during the winter to favour the freezing process while the organic layer in
the summer provides insulation against the thawing energies. At the shoreline of Hudson
Bay, the thin layer of organic material with sandy soils provide an enhanced soil thermal
conductivity that allows greater extents of thawing in the summer and freezing in the
winter; however, since the shore areas are located further north and experiences a cooler
climate than in the southern lands allowing for permafrost favourable conditions. Overall,
permafrost in the Hudson Bay Lowlands and shores are expected to remain present. With
continuing warming trends, it is not unreasonable to conclude the possibility that there
may be a future shift at the southern extent of the subarctic in Northern Ontario to be
reclassified from being a continuous permafrost zone to the discontinuous permafrost
state, and a further shift of the current discontinuous permafrost zone in the south to the
sporadic permafrost state. Future studies in the southern extent of the subarctic should
monitor for indicators of permafrost degradation as referenced in French (1999) for: (1)
increase in active layer thickness, (2) increases in permafrost degradation, and (3)
evidence of slope and active layer failures.
105
6.2 Palsas
Based on observations in the field, this research has incorporated palsas into this
research. Thermal offset results have shown that soils high in organic matter content can
reduce the soil thermal conductivities to provide a layer of insulation for the permafrost
below; this process has permitted the formation of palsa features on the arctic terrain
(Table 23; Seppälä, 2003; Kuhry, 2008). The exact role and characteristics of palsas have
not been widely studied in Northern Ontario; however, observations of these unique
formations have shown ecological and habitat significances for Polar Bears in the region
(Brown, 1973). The dominant physical processes governing the presence of palsas were
identified as thermal conductivity of peat, snow cover and wind speed (Brown, 1973;
Seppälä, 1986; Seppälä, 2003; Kujala, et al., 2007; Vallée & Payette, 2007; Kuhry,
2008). The results from this research concluded that peat layers have the least soil
thermal conductivity in comparison to sand and clay soil compositions allowing the peat
layer to provide insulation against thawing energies in the summer. The presence of snow
cover in the winter and winds proves detrimental to the presence of palsas as snow cover
insulates against freezing energies in the winter from thickening the underlying
permafrost (Seppälä, 1986). Wind actions deposits snow against the palsas and can
provide additional erosion actions against the palsas reducing the structural stability
favouring degradation (Brown, 1973; Seppälä, 1986; Kuhry, 2008; Zhang et al., 2008b).
Since Polar Bears tend to establish dens or utilize palsas for cooling purposes in the
summer, it is possible for Polar Bears to assist in the degradation process by the removal
of the insulating peat layer and by exposing the permafrost to the atmosphere. Changes in
the permafrost can alter the landscape and drainage network affecting food sources for
106
biota and change population distributions (Dyck et al., 2007; Callaghan, 2008; Crompton
et al., 2008). With continuing warming trends, it is not unreasonable to conclude that in
discontinuous and sporadic permafrost zones, the most likely location to observe
permafrost would be in areas dominated in organic material and sites beneath palsas
(Brown, 1973).
6.3 Recommendations for Further Research
Further research on the physical properties of permafrost in the Arctic region will
allow accurate models to predict the presence and potential degradation of permafrost.
With the aforementioned statement, continuous research as part of a long term climate
and permafrost monitoring program and network is recommended to establishing a
continuous and accessible database of permafrost measurements for Northern Ontario.
Long term monitoring of the climate conditions can be accomplished by the deployment
and installation of portable weather stations within the study area that are connected to
data loggers to record continuous air and soil temperature measurements. A second
recommendation for further research is the application of geophysical methods and tools
to compliment field investigations and soil sampling campaigns to provide better
resolution of the active layer thickness, depths to permafrost, soil moisture contents and
actual permafrost thickness data. The use of geophysical methods and tools allow
measuring physical properties on a broad spatial scale and the collected data can be
applied to Geographical Information Systems (GIS) to produce maps, regional
distributions and models of permafrost. This can provide a better understanding of the
permafrost state for civil engineering projects in the northern First Nation communities.
107
Finally, a third recommendation for further research is to focus on the dynamic ecological
and environmental importance of palsas in Northern Ontario and to map the distribution
of palsa features with GIS. Since palsa-polar bear interactions have been observed at
palsas, possibly in search of a den or for cooling purposes, detailed assessments and
research should be conducted to provide better knowledge of the impacts of climate
change on polar bears in this region (Figures 19 & 21). Further research in permafrost
and palsas will not only benefit the academic community but also for those currently
residing in Canada‟s Arctic and Subarctic regions where transportation, resources, and
infrastructures depends on understanding the state of permafrost.
108
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APPENDIX – Additional Figures
Figure 19 – Excavated Palsa located in a vegetated region in Northern Ontario. Digital
photo taken by William Gough, July-August, 2007. Note: Exposed internal core of the
palsa, possibly due to Polar Bear activity in the region
Figure 20 – Soil Samples baking in the oven at 105˚C for gravimetric soil moisture
content analysis: oven drying in the Science Wing Room 313 Laboratory. Picture was taken
on 4 OCT 08 by A. Tam.
116
Figure 21 – Three male polar bears in Northern Ontario, August 2007. Digital photo was
taken by William Gough.